Although, I prefer to on PC exclusively (even if the ports suck) so all I can say is it's mostly preference.
I found the mouse and keyboard controls rather obtuse and clunky, much like the later Dungeon Siege 3; definitely recommend a gamepad for this one if you go PC.
It is also worth noting, that the PC version suffers from some weird glitch that I have yet to find a solution for, especally one that does not include using hex editing. There are parts where you have to talk to a couple summoned NPC's with lots of particle effects and the framerates just DROP. I'm talking from 70+ to 5.
In a convulted way to answer your question, the PS2 may oddly be the superior version but hey, that's just me. Also, the PC version comes with the original 3 DOS games from way back if you are interested in old classics like those.