The included Fractal Design fans are better. The R3 fans are suitable for either air or radiator cooling and are quiet and have good static pressure.
The Phanteks MP fans are some of my favorites, while the SP versions are decent, better than most other included fans, though not quite as good as the Dynamic R3 fans from FD.
I also have to agree with Beaverton. The Arc Midi R3 with 360mm radiator mount up top, removable optical bays and the expansive side window of the Define S would be oh so neat-o. I especially like the movable front 3.5" bottom disk cage, which is a better implementation than the Define R5's.
I very much like the Enthoo Pro-M especially in green, and would definitely consider it if it weren't for the fact that I already own nearly 20 cases already including the bigger brother in white and black.
:doh:
I also like the fact that when outfitted with twin 360mm rads, the Enthoo Pro-M would keep good, solid structural rigidity because of the lower PSU cover, something that the Enthoo Pro (non-M) lacks in spades.
In terms of this comparo, I'd take the Enthoo Pro M. I like the top fan filter, something the Define R5/S lacks, as I use the top rad mount as intake in larger cases like these, and exhaust in smaller cases. I prefer the "S"'s window though, as why go heavy WC without being able to see your nice expensive reservoir, acrylic tubing, and modded pump?