Wasn't quite an argument, but I do see justin3009's point.
ePSXe seems to run better then pSX for me, maybe it's just because I've been using it for so long and know the plugins well. pSX just doesn't seem as good to me, there's nothing tragically wrong with it, but it's running kinda glitchy on some spots for me. Maybe it's just not working for my comp very well (Sadly, I have Vista, with my new comp >.<), I don't know, but like I said:
"MY" final answer:
ePSXe is better, if you're not lazy.
pSX is better, if you never wanna mess around with plugins.
Honestly, in comparison to the real thing, neither match up. So really my suggestion is stop using an emulator and go get a PS1, then you need not worry about any bugs or anything, ever. A PS1 runs like a PS1, no matter what.