[mehulved]

Cos fedora packs in a lot of software in the DVD/CD's. Whereas ubuntu likes to keep it at minimum. But if you look at the final availability of optimised packages for both the distros, online, fedora has just about 8000-9000 rpm's compared to 18000+ for ubuntu. Fedora has just 1 DVD/5 CD's compared to debian, from where ubuntu is derived, which has 3 DVD's/14-16 CD's.
And for 32 bit v/s 64 bit, there was a nice discussion b/w eddie and mediator on the topic. It should be on the first or second page. No need to get into the geeky discussion. Just read the conclusion and select what suits you.