What case are you using?

Obviously, 280mm + 360mm would be the best, but some cases have a few clearance issues in that regard. If you're using very vibrant RGB fans, you might want to use 2x280mm just for evenly sized fans.

You can fit a 360mm rad in the front of the Define R6 HOWEVER you will not be able to fit an optical drive in the case with it. a 360mm rad may also interfere with an optical drive on the top config as well, so keep that in mind if you were wanting an optical drive for your build.

aside from that either configuration should be fine