Sports Car of the Year: M135i vs Boxster

The Stig is coated in Teflon. This is possibly the only answer I can provide, given that he's just appeared striding across a recently ploughed Lincolnshire potato field, yet has arrived spotless, eye-cringingly white, his race boots unsullied by the thick mud. As ever, he simply marches up and holds out a hand, demanding keys. And, as ever, I try to engage him in conversation and get absolutely nothing in return, except for a slightly impatient beckoning motion and a sense that I am, somehow, an imbecile. So I toss him the keys to the Porsche, and watch as he snatches them perfectly out of the air while looking the other way. He then walks up to the Boxster, slides into the seat, prods every available button to maximum - except for the PSM traction control, which he disengages - dials up about 4,000rpm and exits in an acrid flurry of tyre smoke. The little Porsche howls in delight, the rest of us just stand there and watch.

Photos: Matt Howell

This article originally appeared in the December 2012 edition of Top Gear magazine 

A few minutes and several - ahem - extremely rapid and tidy laps later, he slams to a stop in exactly the same place and the process is repeated. I lob him the keys to the BMW M135i and he slithers away, the white 1-Series's turbo straight-six a guttural counterpoint to the Porsche's flat-six yowling. The BMW looks more of a handful, but The Stig seems to be able to collect even the most ridiculous slides with ease. And then he's back. But he seems somehow... undecided. He looks at the two cars, and cocks his head slightly, like a very scary puppy. And holds out his hand again.

We can forgive the indecision. Because as much as TopGear enjoys a good argument, in 2012 two cars have stood out as being exceptional in the loosely termed Sports Car category. And the pair fought each other to a standstill in the office shouting that constitutes our peculiar electoral campaign system. Those two cars were the BMW M135i and the new Porsche Boxster. Which obviously required a decider, no-holds-barred, road and track, plus Stig. And yet, The Stig, usually a proponent of instant non-verbal decision-making, is heading back out (again) to try to get to grips with which of these two he prefers. Which, at the very least, confirms that we were justified in our confusion.

Of course, it looks like we're making the mistake of comparing fish with horses: one car is a two-seat, mid-engined sports car with natural aspiration and a decidedly slinky demeanor, the other is a slightly frumpy hatchback with a big turbo motor and four seats. But look more closely. They're both reasonably sized, rear-wheel drive, six-cylinder, premium cars that hit 62mph from rest in the fives. They both comfortably exceed 150mph, and are aimed at the kind of person that - while they enjoy driving - also sees the value in day-to-day utility with a dash of quality. Real-world cars for real people. While The Stig is continuing his assessment, I decide to chase him. He's left me with the BMW, so I fire up the 3.0-litre twin-scroll turbocharged straight-six and follow him out.

The little BMW is - frankly - a bit of a shock. It might look a bit dowdy, bespoke wheels and large blue brake calipers aside, but the effect of 320bhp in a car that weighs 1,500kg is punchy to say the least. It's eyebrow-raising fast. But that's not even the real story, because the way this car unravels itself up a road, with 332lb ft available from a remarkable 1,300rpm, means that it feels earthquake brawny - the torque making the biggest impression from the driver's seat. The car we have here is equipped with the optional £1,600 eight-speed automatic which drops the 0-62mph time to just 4.9 seconds. And it's brilliant, surfing the torque and flitting between ratios, but the overriding impression is that the BMW feels like a little muscle car: big engine, small car, enthusiastic cornering attitude. In these slightly damp conditions, it's ridiculously tail happy, although it hasn't got a traditional limited-slip diff. There's an Active Differential Brake (ABD) in Sport mode that restricts torque to the spinning inside wheel, and an electronic diff lock in DSC-off mode, but neither really gives the impression of aping a mechanical locker. Mind you, in the dry, it's less aggressive than a traditional locking diff - as found in a full-fat M car - and thus possibly less effective, but in the greasy damp, you can slide around all day and then fail to kill yourself even when the rain clears.

That's not to say the BMW hasn't got skills though. The M135i sits between the M Sport styling and suspension grade and a full-on M car, niching itself as M Performance. So it gets bespoke suspension, the tweaked engine, big brakes and a few other bits that make it stand out. It translates as a car that's softer and easier to handle than a full-on M, but much punchier than you expect. Which makes it a real road weapon - soft enough to cope, fast enough to scare yourself silly if you feel like it. It's good on the track too, though the variable-rate steering - standard on the M135i - can give mixed messages when you're flippering madly from high-speed, looping S-bends to tight chicanes. It also feels slightly numb - there's a surprising lack of understeer, followed by easily provoked oversteer, but it might be even more fun if you knew more instinctively what those front tyres were up to. It's supple on road, but unsurprisingly feels a little soft even in Sport Plus mode on track, still with sticky-footed levels of grip if you try to be neat. But it's noisy and up for it, laugh-out-loud fast and fun. In a way that it never looks like it will be. It is, for all the BMW cliches, a proper little demon and absolutely brilliant.

A few laps later, The Stig simply forces me to a stop by parking in the middle of the circuit with the door open, and I'm prised unceremoniously out of the BMW. So I hop into the little Boxster, and get confused all over again. Mainly because this isn't anything like the BMW. At all.

For a start, the 2.7-litre is naturally aspirated and swaps turbocharged grunt for deliciously precise throttle response. You have to rev the Boxster all the way to the red line to really make it shift, and it never has the sodding great wave of torque that makes the BMW so punchy on the road. But it's sweeter and more tuneful, and you snick between ratios and rev-match downshifts almost instinctively. You sit lower, and the steering is more transparent than in the BMW, allowing you to play within the limits of grip with more confidence. And the mid-engined layout has more natural balance in the first place, so you push harder and harder without really noticing. In the BMW, you end up having a polite wrestle at very high speeds. The Boxster simply gets better and better the more you push. Most startling is the lack of understeer in even the tightest of corners, the Boxster nailing itself to whatever you point it at, with just a graceful exhale of oversteer through a corner exit. It hasn't got a limited-slip diff either, but never really feels like it needs it, because the relative lack of torque doesn't really upset the car as much as the BMW's typhoon mid-range. The only real thing you consistently think is that the chassis is so talented, it could handle more power. A lot more power. Which is a huge compliment.

And here's the kicker: the Boxster is no slower around this little circuit. It might have 55bhp and 126lb ft less to play with, and be just under a second slower to 62mph, but it weighs 115kg less and has a fluidity the stubby M135i can't match. It finds grip and finesses it, where the BMW digs and claws. An object lesson in mid-enginedness. It's the best sports roadster on the market right now and I'd go so far as to say that it's a better pure sports car than the BMW M135i, full stop.

This has confused The Stig, who batters both cars around the track until the Porsche is running on fumes and the BMW is trailing round tyres that have suspicious little canvas bits peeping through like an untucked shirt. Neither seems to gain a definitive performance advantage and The Stig simply screeches to a halt mid-lap, stares hard at both cars, and stomps off to wherever it is that he goes. As he leaves, a small puff of exasperated smoke wafts out from underneath his visor. Funny that, because before we got here I thought he'd prefer the purity of the Boxster, even through the exciting fug of BMW lairiness. I thought that there'd be considerable decision weight in its mid-enginedness, and the fact that when you think of a sports car, nine times out of 10, you'll picture something Porsche-shaped.

But the Porsche doesn't win this test. The issue with the Boxster is that it's actually not very surprising. It is the best roadster, and it is a masterclass in dynamics. But we expected that. We'd have been mortally offended if it wasn't. And you pay for the brilliance - you have to shell out £37,589 for a base car, and it doesn't arrive with a glut of standard kit. The straight manual Boxster we had here was relatively lightly specified, and still came out as costing just under £50k. Which is mental, when you really think about it.

But the Porsche doesn't win this test. The issue with the Boxster is that it's actually not very surprising. It is the best roadster, and it is a masterclass in dynamics. But we expected that. We'd have been mortally offended if it wasn't. And you pay for the brilliance - you have to shell out £37,589 for a base car, and it doesn't arrive with a glut of standard kit. The straight manual Boxster we had here was relatively lightly specified, and still came out as costing just under £50k. Which is mental, when you really think about it.