For high-end gaming Sand-E is likely to be better (quad channel support, etc). I don't plan on building my next rig until fall and I fully expect to be buying a 3930K on asus's rampage board.
edit: I echo what lemlo posted about multi-gpu setups. And also, preliminary reports (more info will come in the next few weeks ofc) suggest Ivy is actually running hotter than Sand-E's.