As a general rule, 8 vs. 10 MP doesn't really matter. It's not something to base your decision on. However, It's normal for ISO 1600 to be noisy, and of the two cameras, the Canon handles noise the best. Another thing, the 30D is on a higher level than the a100. The a100 should be compared with Canon's 400d, and Nikon's D80.
We're saving for a new dSLR for my husband. "Semi-pro" is probably the best way to describe him as a photog. He designs lighting for theater and dance, and takes portfolio, archive, and advertising shots of performances. Good performance in low-light situations (under tungsten stage lighting) is a must, as is accurate depiction of light and shadow, and color saturation.
I'm considering the Sony AlphaDLSR-A100K and the Canon EOS 30D. The Sony we could afford now, the Canon would take a little more saving up . . .which might waiting until after his next show and therefore missing the opportunity to shoot that one.
The Sony offers 10mp versus the Canon's 8, but I'm concerned about the reviews noting noise in photos taken at ISO 1600. It states that the noise is manageable when taking raw shots and using the noise-reduction software, and that it might be acceptable for prints up to 11x17. He would not be likely to print larger than that, and usually not larger than 8x10.
The Canon goes up to ISO 3200 and the reviewer notes that shots all the way up to that limit are clean enough to produce good-looking shots.
"acceptable" and "good-looking" can be so subjective, so I'm not sure what he really needs here. Will the Sony give him impressive portfolio shots, or is it worth it to save a little longer and go for the Canon?