Big Bow window replacement...need advice

DH are easier to operate and clean.

Casements are more airtight, better thermally (not as much bridging with more glass), more ventilation area, harder to clean unless you have a center hinge.

+1 to anthony and WoW's comments... Personally, I'd probably prefer the DH unit in something of that size, despite the slightly lower #'s. I can't speak for others, but I've personally seen more service issues in larger casements. Next month I'll be replacing one that was caught by the wind and literally ripped off the hinges... Although to be fair, this was a cheapo, new-construction unit.