Canon EOS Rebel T3 (1100D) or Nikon D3100?

Which one is better for a beginner photographer whose had a Nikon P90 and is ready for an upgrade? I want one that takes clear pictures, has a good zoom, and a good focusing lens

Nikon d3100
but if you have the extra money, go for the d7000.

The D3100 is better. It has 14.2MP vs 12.2MP on the T3. And it can shoot
1080i HD video, the Canon stops at 720. The kit lens from Nikon is
better too.

There's no clearer camera. I mean what, we can't just say Nikon has 14% better performance but makes everyone ugly.

Good zoom depends on the lens you get.

Good focusing lens; well all DSLRs are great and lenses as well. Unless you buy some cheap used fake of course.

The D3100 costs more and thus gives a little bit more options, such as Full HD vs HD recording, slightly better high ISO performance and that's it.

Here's a DSLR Buying Guide - http://www.the-dslr-photographer.com/2009/11/which-dslr-to-buy/