Obviously the PC version is going to be far superior in many ways. For a start, besides the finer graphics, there's more content as with the Xbox360 & PS3. In fact there's quite a bit omitted in the PS2 version. So if your PC can handle it then I suggest you get that version.
However there's a big but... It needs a high end PC to handle it. My PC has got all the qualifications except for the graphics card. It's a 256MB integrated card and I'm afraid it just won't cut the mustard. The rest is fine. AMD 64bit twin core 3GHz CPU and 2GB of RAM. So I had to get the PS2 version. Unless one day I invest in an acceptable graphics card.
So if your PC is up to scratch, get that version. If not then get the PS2 version. You'll still enjoy it, but you can't help thinking it's all geared up for the new gen machines and that something is missing.