With a Steel framed 1911 I like Chip McCormick PowerMags.
+1. You can buy more expensive mags than those Chip McCormicks, but you can't buy any that are more reliable. I bought a couple of Power Mags and Shooting Stars and they have been 100% reliable in my Springfield.
It's funny, but my buddy has Power Mags as well and he keeps jonesing for a Wilson Combat mag because "they are supposed to be the best." My response back to him is, "what will they do that the Chip McCormicks won't do?" He has no answer for that one as his McCormicks have been 100% reliable as well.
As far as 7 or 8 round mags, its your choice but there are no draw backs or advantages, other than an extra round, between the mags.