1) Fit and Finish. You cannot say with a straight face that the Volt has an interior worthy of an Audi or BMW. In fact, my wife's new top of the line CRV has a better overall interior than the Volt.
2) Performance. The Volt doesnt even come close to the performance of most european luxury sports sedans.
From experience I can tell you that (1) the interior of a BMW is nothing to write home about and (2) I've had plenty of ultimate driving machines disappear as small objects in my rear view mirror. I'm not saying the Volt is a fast sports car, but in daily driving about its only peer is the Nissan Leaf. And it's not just me. In fact a couple of weeks ago I was sitting at a light going South. At the light going West there were three cars abreast. Two BMWs and a Nissan Leaf. When their light turned green the Leaf left both the BMWs behind. It's just the way it works as a practical matter. Yeah if you went to a track you'd get a different result but people don't drive at the track. They drive on public roads with traffic lights.
As for the interior, the Volt's interior may not use expensive materials but it works. I had a artist friend who drives an MB want to check out the Volt. She got in, just sat there, and then she said "this interior makes my Mercedes seem old and tired." Some of that may have been she was expecting a Cimarron, and yes the Volt interior has some nasty plastic edges, but for a car with cutting edge technology the interior does a good job of projecting what the Volt should be. I've also never seen the cloth interior so maybe that's a different story.
As for the BMW interior, that's kinda a joke. It was just basic and the controls were goofy. I hated the fact that you not only had to have the fob, but you had to put the fob into the steering wheel. Are you kidding? I'm also not a fan of all the buttons on in the Volt but i-drive takes bad interface design to new heights (or depths). If you check out the BMW 5 series over at TrueDelta what you'll find is that those who bought a BMW 5 series did so because of it's "smooth acceleration" and "great 22 MPG gas mileage" and "massive torque".
http://www.truedelta.com/BMW-5-Series/owner-reviews-20 The interior is never mentioned (for that you have to go to "Why Not the BMW 5 Series" where you'll find people derisively and unfavorably comparing the BMW 3 interior with a Honda Pilot's). But all of these advantages are exactly the advantages the Volt offers. In fact the only area where I think the BMW has the advantage is in the suspension, which is way better than the Volt's. But if you're looking at "smooth acceleration" or "great MPG" or "massive torque" the Volt has the BMW beat. (FYI we got the leatherette not the leather seats on the BMW, mostly because they breather better, require less maintenance, and wear better, so you can factor that into what I'm saying.)
As for what cars are being turned in for a Volt, there are probably 50% more Priuses on the road than there are BMW 3 series, and certainly a lot more than there are BMW 5 series, which is to me the more natural comparison because of the mass and the way they handle. If the rate of adoption is the same then you'll naturally end up with more of the more common car. It's just the numbers.
