Dunno, I played both demos for a few days now and I must say that I still prefer PES.I'm not a big fan of soccer games but I have PES6 and it's a very fun game to play online or with another person, although I always liked Fifa better because of the licenses. I wanted to get rid of PES forever and ever as a franchise and no I have good reasons to do so. Thank god
What impressed me the most about PES6, in general, was the naturalness of the game, since some things looked logical compared to real life, and that's not easy to achieve in a (sports) game.
Now, in PES08, the faster pace of the game destroyed that and it's as unrealistic as uninteresting, it's so fast it makes no sense. That's were Fifa 08 stands out, the pace of the game is very realistic, perhaps the most rational soccer game I've ever seen in that regard. Also, the graphics are better but Fifa's graphics has been always better in comparison with PES, so that's a minor point.
Fifa 08 features more game modes, leagues, licenses, better control (with everything in Manual you are the maximum responsible of good choices and mistakes) and you don't feel like you are playing basketball instead of soccer since, on the contrary to PES, the scores are "logical", because of the aforementioned pace of the game. EA need to tweak a couple of things; the ball-going-in-net animation and CPU's overpowered free throws, but other than that Fifa is superior (imo).
So, if I ever purchase a soccer game again, welcome EA, bye Konami. Anyways, as I already stated at the beginning of the post, soccer games are not my cup of tea.
FIFA looks quite a bit better, will have more licenses, the animations are better (what amazed me is how the managed to capture the individuality of the players in motion) and the pace of the game is more realistic, but it still lacks something. Maybe I just suck at the game, but in most of my matches I didn't really manage to create any exciting scenes in front of the goal and neither did my opponent.
Most of the time was spent running up and down the midfield, carrying the ball around and waiting for players to move into good positions for an attack - which hardly ever happened. The AI seems kinda dumb that way. So while the overall pace and feel impressed me, it just lacked any real sense of excitement and even the few goals that were scored felt kinda dull. I'm gonna give it a few more tries though...
PES2008 on the other hand is pretty much exactly the refinement of the series I was looking for. Nothing spectacular, but doing away with many of its predeccessors shortcomings and still featuring the trademark gameplay at its core, which - despite actually being more arcady this time around than FIFA - still captures the excitement and ebs and flow of a real football game like no other.