i thought the I6 was inherently smoother than the V6 which is why BMW has been populating its cars with them for ages..

also i believe i read somewhere that the less cylinders you have, the faster the engine can spool up. hence the popularity of 4-cylinder high-revving engines for applications such as WRC where there's a lot of "up and down" speed as compared to NASCAR where you just go round and round at high speed.

niky, you also forgot the mutant W8, W12 and W16 engines that VW is so fond of