For win32 versions of mame, either should work fine.
Regardless of what sound option you go with, you need to be concerned with CPU utilization. If you're running a low powered CPU to start out with, having a bad sound chip sucking up CPU cycles can really hurt.
In general, onboard sound uses more cpu cycles than PCI sound cards, but this is not always the case.
You might want to borrow some sound cards from your friends and benchmark them against the onboard sound to see if the framerates suffer.