Outperforming is subjective.
I'll say that build quality is better, it gives a more solid feel, AF speed, burst rate would be faster if it matters, faster operations in terms of adjusting settings and so on. After all it is designed for a more professional group of photographers as compared to the 450D. Prism should be better if I remember correctly [higher coverage and magnification]. If I were to comment on image quality, i'm sure i'll open a can of worms...so I won't.
Let's just say that the 30D is a very capable camera at a very reasonable price right now. Do expect it to have higher demand for it and less depreciation as compared the to 450D should you decide to resell. (: The $200 difference can be spent on a good lens, which usually matters more than the body.
Umm, regarding the MP issue, correct me if I'm wrong, I think 2MP is sufficient for 8R prints. Of course you can crop and edit more with more MP, but the idea is if you have less room for error, you'll start making less errors, which is the whole point of learning photography. 8.2MP is more than sufficient for most uses and it'll save your computer some memory space as well.
You might want to do a comparison between the 2 cameras yourself. Check out www.dpreview.com for camera specifications.