I had a 300ex prior to buying the 400. I never *really* needed more power but i'll have to admit I kinda craved a bit more than the 300 would give me. I have never rode a raptor although my cousin just bought one so i'll get my chance soon. I read reviews, and asked around the message boards mostly. What really made my buy the 400ex was the dimensions. The raptor is taller, narrower, shorter, and heavier. I didnt want any part of that. I only weigh 140lbs, so pretty much anything above 300cc's is going to toss my ass around easy. I went for the stability and the proven reliability.
I do love the looks of that 660r though, and miss the reverse. I hope they change it a bit and make the center of gravity a bit lower, that's a HUGE issue. I could tell just buy sittng on one in the shop that it felt wrong for me. I'll actually get to beat on the 660r this week if I remember i'll post back here even if the ride proves me wrong. =) I kinda hope it does.