DPREVIEW is an excellent site if you're not aware of it. Page below summarises the 2, but there'll be mountains of other info including in depth reviews and forum feedback on them. Both an excellent entry to DSLRs. I've been very happy with my 450D for astro and terrestrial.
http://www.dpreview.com/reviews/comp...1000d&show=all
If you're only or mainly interested in astrophotography, might be worth reading up here on 2nd hand modded DSLRs (UV/IR filter removed or modified) as sensitivity to hydrogen emission nebs in particular much better.
I wanted a camera that could work quickly (without white balance fiddling) as a "normal" terrestrial camera when I bought, in case I turned out to be the world's worst astrophotographer!
Canons certainly seem to have been the traditional pic for astro work because of relatively low low light noise.