I use the American Crafts brand. I absolutely love them! Yes, they hold lots more pages than a regular post-bound album. I'd say I can get more than twice the amount in them than I can in a post-bound album. The rings do stay closed tight. You can fit all different size pages in a 12X12 album, too.
The only (small) con to using them is that your pages won't line up side-by-side like they do in a post-bound. This would only most likely bother you if you do a lot of double-page layouts. I do a few double-pagers, and it doesn't bother me at all.
I highly recommend them!