Which feature is the best out of these?

Certainly not the shop. I like the idea of unlocking flaming powerbars (PSP version) and medals so your opponents in multiplayer can see what you have done but I would have prefered all the soundbanks and pretty much everything else unlocked from the beginning. I was going to finish all the missions anyway, the medals, challenge and even cut scenes were enough incentive.

I have the DS Version, and i like the puzzles the best. I have never been online, because i don't have a DS wifi connector!