I like when both are implemented. Not because it's better or anything, but because it makes the most sense. Unlimited storage only being hindered by weight is stupid (you'd look silly with 5000 pounds of junk hanging off of you). However, on the other hand, having limited storage, but being able to carry anything is just strange, like in WoW, when you kill a giant demon/boss, and bring his head back for a quest which is 10 times bigger than you. However, a mixture of the two makes the most sense, making it so you have to earn more storage space, but it doesn't matter because you can only lift so much.
I want a game that makes you progressively slower the more you pick up (Oblivion, and Morrowind have this in a sense, but you just stop moving once you pick up too much.