I've been pondering the same. I much prefer 6-prongs. To me, 4 prongs on a round diamond looks odd, especially with smaller stones. But, the problem is that 99% of the settings out there for rounds are 4 prong. I also like pretty details on the basket, especially lots of pave, which is harder to do with the more cramped 6-prong designs. I keep trying to convince myself about 4-prongs, but I'm not there yet.
I would also love to see some unique pave designs.