Try the 3.0sd - you'll never even see the 3.0d in the US. You absolutely _can_ compare them, and the 3.0sd will blitz the 3.0si every time. You'll forget all about the 3.0si and it'll be the 4.8 that you'll find yourself comparing the 3.0sd to.

The only negative, if you could even call it that, is the idle sound.