The 270 and the 270X use the exact same chip with 1280 shaders. The 270 has a TDP of 150W and the 270X of 180W, but if you clock them at the same rate, they will perform identical and use the same amount of watts. If one card gets 15 degrees hotter, well, the cooling systems of graphic cards differ a lot and the poor ones show under extreme stress like an oclhashcat run.
The reason why the other guys perfer reference design is the fact that reference design cards use an radial cooler while OEM designs use axial coolers. Hence more effective the axial cooler just spins a lot of air around and does not care where it came from and where it goes to. The radial cooler tries to get the hot air out of the system at the back of the GC. If you stuff two GCs with an axial cooler next to each other the one with its cooler next to the back of the other is heating that card up. If you can leave a lot of space between those two and you bring a full package of air flow into the case then these cooling solutions might even work. But with four or even eight cards you have no other chance then using reference cards with a radial cooler.
The reason why the other guys perfer reference design is the fact that reference design cards use an radial cooler while OEM designs use axial coolers. Hence more effective the axial cooler just spins a lot of air around and does not care where it came from and where it goes to. The radial cooler tries to get the hot air out of the system at the back of the GC. If you stuff two GCs with an axial cooler next to each other the one with its cooler next to the back of the other is heating that card up. If you can leave a lot of space between those two and you bring a full package of air flow into the case then these cooling solutions might even work. But with four or even eight cards you have no other chance then using reference cards with a radial cooler.