So, AMG junior is here then...It certainly is, available as either A45 AMG or CLA 45 AMG. Here we're going to concentrate on the CLA, because although Merc says that underneath they're borderline identical, separated by no more than different spring/damper rates and a couple of desirable options, in fact these two, in the spec we drove them, are surprisingly different. But leaving that aside for a moment, this is a very different type of AMG.How come?Well, until now, the power saloon has been AMG's baseline. The C63, the E63\: thonking great V8 up front, a rear axle that struggles to cope and plenty of fireworks for all concerned. This is different, this is a hot hatch. Or a hot sleek small saloon or whatever it is we're meant to call the CLA. Besides ugly.But it's got 354bhp...Yep, and that's the same as the 5.5-litre V8 E55 AMG developed not so long ago, only here it comes courtesy of a plain 2.0-litre four cylinder. With a turbo. A pretty big turbo, it must be said. Power goes to all four wheels through a seven-speed double clutcher and a series of differentials. But not permanently. In fact until the front wheels start to slip, this is a front driver.So how does it cope?Pretty damn well, due to the fast reactions of the on board computers in sending power around the place. In fact it's a ridiculously rapid cross country device - the chassis is perfectly able to cope with the power and body control is superb. But in the CLA the 2.0-litre turbo never feels like it's doling out the full 354bhp and 450Nm. Both this and the A45 have the same claimed 4.6-second-to-100kph time, but the CLA is porkier by 30kg, in fact just porky full stop at 1585kg, and has a marginally less focused demeanour.What do you mean by that?That the CLA isn't a hardcore car. This is the one that's aimed at America (where they won't get the A45), and that means the dynamic edges have been rounded off slightly. Even if you opt for the sports exhaust, it's quieter here than in the A-Class. Our one didn't have the sports exhaust (nor the sports suspension) and bar a pop on the upshift and an occasional chatter on lift-off, aurally the engine was a bit of a disappointment. This is concerning, because if AMG can't make a four-cylinder turbo sound good, what hope for others?But the Audi RS3 sounds pretty good, doesn't it?It does, but it has a fifth cylinder to inject some character. The BMW M135i has an extra pair. Those two, plus the new S3 and old 1M are the cars that Mercedes has been benchmarking. Of them, the Mercedes feels more aligned to the Audi - a fellow transversely-engined 4WD car, and one that majors on cross country speed rather than outright pleasure. The CLA is very quick and very competent, but competence is sometimes an over-rated trait. It's not a particularly engaging car to drive. Partly this is down to the lack of noise from our car, partly to the marginally (but noticeably) softer suspension, but either way I got out of the CLA feeling more downbeat than I'd hoped to. Don't get me wrong, it's less nose-heavy than the RS3 and rides significantly better too, but this is still a car with its engine ahead of the front axle and an obedient tail.And what about the gearbox?No manual, instead a seven speed double clutcher. It's OK, does what it needs to do and isn't overly obstructive unless you try to downshift at high revs. Or move quickly from forwards to reverse. The bigger issue is the gaps between the ratios, specifically between third and fourth. Closer spacing would make the whole car feel punchier, more accelerative and exciting and would have helped mask the noticeable lag from that big turbo. I'm guessing that emissions were a significant consideration and, fair play, the 354bhp CLA claims to be cleaner (161g/km) and more efficient (14.4kpl) than a Ford Focus ST (which has over 100bhp less).That's not really the point is it?No. If I'm honest I wanted the CLA to be naughtier, and since I drove it before the A45, it made me concerned for that car as well. But it is swift and AMG has done an amazing job of making a small capacity engine very smooth and drivable with no spikes in the delivery. Remind yourself that the only other engines we've seen like this were in cars such as the Impreza STi and those Lancer FQ models, which basically got down the road in a series of explosions. This one will pootle and won't bite. But neither, in the CLA, does it truly excite.What's the verdict, then?Six out of ten, borderline seven. The lack of a proper soundtrack was disappointing and it, even before options, will cost a chunk more than the A45 AMG.