I prefer sumo, and the taller you are, the more it will decrease your ROM (which is a good thing if you're a powerlifter). I remember Amy W. failing a 500+ attempt because her ROM is SO short that she was able to bend the bar up to lockout without the weight ever even leaving the floor! hahaha...
I think it's a good idea to practice both. I know when I do conventional it reveals some weaknesses I don't see when I pull sumo. When the weight gets serious, though, I pull sumo because that's what I'd do in a comp.
Sumo will recruit more leg/hip strength; whereas, conventional will recruit more lower back strength. They're both total body moves, though.