In theory, it should not make a difference. However, in practice, it may make a difference. The more channels you have in one box, the greater the possibility that there may be electrical interference between the channels. One box also increases the possibility that the power supply is insufficient in size for all of the channels at once. It also increases the possibility that with one plug in one wall outlet, the circuit may not be able to provide enough current for all of the channels. It becomes a question of the design of the particular unit, and your house's electrical circuitry. With isolation of channels, a sufficiently large power supply, and sufficient wall current, then a single amp would be okay. Otherwise, it might be better to have multiple amps plugged into differrnt circuits. So the answer to your question will depend upon the particluar amp(s) being considered, what speakers they are driving and what it's all going to be plugged into.
It should also be noted that it is important to keep speaker cables short. All other things being equal, it's better to have long interconnects and short speaker cables than the other way around. With this logic, it would be better to have the three channel amp driving the front and centre speakers since the amp could be close to all three. Then sit the 2 channel amp somewhere in the back where it could be closer to the surrounds.
It should also be noted that it is important to keep speaker cables short. All other things being equal, it's better to have long interconnects and short speaker cables than the other way around. With this logic, it would be better to have the three channel amp driving the front and centre speakers since the amp could be close to all three. Then sit the 2 channel amp somewhere in the back where it could be closer to the surrounds.