Oops sorry yes I meant the CPU not the PC.
Regarding the difficulties, when I was playing PES 5 a lot on PS2 back in the day I had this conversation with Victorious (maybe wrong spelling) and Lukas (Soyo) who both used to really push WE9LE as the best PES. I tried it on PC along with PES 5.
I found both WE9LE and PES 5 on PC easier than the PS2 version. The reason being is that I find the PS2 version less responsive, maybe because of the controls, the system, I am not sure but there is a 0.5 sec delay when pushing the buttons on the controllers compared to PC. So I found that on PC version of both was too easy to do one touch passing and zipping the ball around.
Regarding PES 6, I just don’t like, too easy, too arcadey in my opinion, so played it for a few weeks when I first bought it on PS2 and then I gave it to my mate’s son and went back to PES 5.