@SVL, what Spud said about pixel counts. You need about 5MP to produce 10x8 prints without clever processing. The trouble is that most internet comparisons are the equivalent of ramming your nose against a billboard. At normal viewing distances the differences are much harder to see. I could hand you a stack of prints from 6, 10, 12, 16 or 18MP cameras and you really wouldn't see much in it.

Nikon have been leading at low light performance for a while but again there's really not much in it. The D5100 has the same sensor as the D7000. See http://www.bythom.com/nikon.htm for informed Nikon reviews. Or read Ken Rockwell if you like a laugh