The idea of letting the OS "manage" your virtual memory sounds like a good idea at first, until you think about it a little bit.
I would highly recommend that you decide how much virtual memory you need and set the page file size yourself. The reason being that if you let the OS change the file size, you risk having a very fragmented swap file. It's better to set the lower limit the same as the upper limit. This gives you a constant file size that will remain in the same place on the drive permanently (i.e., no chance of further fragmentation).
Having a single non-fragmented swap space will definitely improve your swap performance.