I disagree, I think 6610 looks better than 6100(6100 is much lighter though)
Well, cons about the 6610 are the small memory size(700+kb), and sometimes slow response, in my opinion
Also, I've heard that theres a flaw in the 6610 design, which allows dust to creep in from the back after 2-3 months use(Can anyone confirm it?)
Why don't u go for the best phone in its price range?The Sony Ericsson T610(2003 'Phone of the Year')
It has a bigger screen and better screen, nice interface, more memory(2MB),Camera,Bluetooth(6610 dosen't have bluetooth),Polyphonic Composer,etc.(Much more features, almost same price)
U can compare them both here-
http://www.esato.com/phones/index.php/phone=74,cp=45