As you may already know, an AIO cooler like the H100i uses its fans to draw cool air across a radiator to cool the liquid inside, so logically, you want the fans in a pull configuration. By using a push configuration, warm air from within the case will be drawn over the radiator. The temperature difference probably won't be much in all likelihood, and the ambient temperature is always the deciding factor with PC cooling.
A push/pull configuration will simply disrupt air flow where the two sets of fans meet, so avoid doing this.
On the basis that you'd use a pull configuration, I'd suggest taking two of the H100i fans and using them as exhausts elsewhere in your case, if you can.