WE6 and PES2 are very much different games. PES and WE5 were probably closer. WE6 had a really good AI system (haven't fully tested WE7 yet so I can't comment).
At the end of the day if you enjoy ripping apart defences with minimal effort and scoring loads of goals at will, then PES2 is the game for you. If you want a challenge get WE6 for a very challenging AI system, where you really have to work hard to score. I know which I enjoy, I don't really care who plays what as long as their playing Konami soccer.
The gap between the 2 series should have been closed with WE6 and PES2 but never was resulting in the larger gap between WE6FE and probably now WE7.