I'm not really a fan of both, but I feel like inventory slots are a bit more thought out than weight systems. I guess when I think inventory slots I think Diablo 2 or Resident Evil 4--it is like a puzzle almost...this is what we're giving you, making it work the way that is best for you. Whereas weight systems just encourage you to pick up every damn thing until you hit the limit and then back and forth dropping crap constantly ugh. Can't stand it.