No website that I know of has such a comparison.
However, here is my list of "good" aftermarket mags:
1. Mec-Gar
2. PMI (for Mini-14)
3. John Masen (ditto)
4. USGI M16 mags, save the bad ones mentioned in the mag FAQ at ar15.com
5. Any 1911 mag made by one of the 1911 custom houses (e.g., Wilson Combat)
Justin