Here's why, in my own decision making, in hindsight, I'm glad I went with 5D2
Liveview: Really useful for getting focus wide open in certain occasions I've found.
Video: I've gotten good use from it
More MP: You may not need 21MP, but I'm really glad to have it especially now that I'm printing more. You can always shoot in SRAW (around 10MP) in situations where it's overkill.
Better LCD: Never used a 5Dc, but I think we can all agree it's bigger and better, no contest.
Auto dust sensor cleaning: Again, never used a 5Dc, but I'm just glad I don't have to deal with its 'notorious' dust issues. Especially since you'll be buying used.
MFA: Although I haven't really sat down to do it proper yet.
Higher/cleaner? ISO: Self explanatory
And the final kicker is I can get the 5D2 new. There aren't any new old stock 5Dc's around or the decision would have been a lot tougher. I don't do used camera bodies.
And the files will eat up your HD much faster, obviously dramatically so if you're doing video.
And keep in mind I came from a 350D and didn't think I 'needed' a lot of this stuff (like liveview) but they are sure nice to have around.