Ok you asked! The size of the capaciter is relitive to the imedance caused by the circuit runs on the motherboard in relation to the expected frequency of unwanted noise in the system. This basically shorts unwanted frequencies to ground (usually 60hz noise from the power supply) It is indeed the quality of the capaciters, namely the material they are made out of , not the specific rating that makes a good cap.
So the overall board stability is more than just the size of the caps.