If you've got only these choices i'd say go for the 3200 as it has everything from the 6610/6100 and a CIF camera also. But there is a small problem that if you keep changing covers often then the shell becomes loose.
Ask this fellow, PM him as he has a 3200. Tell him I referred him to you.
As for info on the 6610 you can ask me as I have it, PM me here
Then you can make your inferences and get an appropriate phone.