I have been playing WE9LE a lot recently having long considered PES 5 the greatest footy game ever made.
WE9LE is indeed a tweaked PES 5. Less fouls, maybe slightly more attacking AI and a few different animations. I wrote on the epic Retro PES thread about how it possibly even surpasses PES 5.
Now, having played it extensively for a few more weeks, I'm here to tell you that PES 5 is STILL the best footy game ever made. WE9LE is great but I gradually found the certain aspects is not as good as PES 5.
The shooting is not as varied. Shots tend to go centrally a lot, making it easier for the keeper save. Maybe to balance this, I started to notice that the keepers are very vulnerable at their near-post.
Also the fatigue system, in Master League especially, is toned down compared to PES 5.
And I know some people hate them, but I actually missed all the fouls and how those harsh refs make you have to consider each and every challenge.
PES 5 - THE greatest footy game from the greatest era of footy games. We will never see the likes again.