Yes, PES is like super fast this year, but the default FIFA is only a little bit slower. Correct me if I'm wrong, but slowing the game speed is WAY easier that making a realistic AI. And I remember that PES have more speed options than FIFA; at something like -2 speed it shouldn't be too bad.
And it's not only about the CPU AI, but also AI on human side, especially in player vs player game. I don't know on what basis EA implemented the "Teammate Intelligence" feature some version ago, but my AI teammates are absolute dumbfucks, both in attacking and defending. Poor distance maintaining, minimal off the ball runs, nearly zero auto marking. It is so frustrating playing with my friends who use the sprint and cross/shoot style of play. The way I play FIFA is very close to real football: very gradual buildup, constantly searching for passes, a lot of back passing, level passing, and changing direction across the field ,very occasional sprinting/crossing. I had a field day with that playstyle in PES 6, and can already see I will have a field day in PES 15.
In FIFA? Well let me tell you a story. My best friend, whose skill in FIFA is about the same level as me, often picks a Ligue 1 team when playing with me, substitute all the black players in (only see image, not overall), and crush me even when I use a 1 star higher ranking team, because all of his players are too strong to stop. Occasionally I become so pissed that I pick a Ligue 1 team back and crush his Ligue 1 team with that same style of play. It's not that I can't play that fast-forward, constant counter attacking style; it's just too boring to play when all of your goals are pretty much the same. Sadly, even I have to admit that it's the most effective style. And it's gonna be the same in FIFA 15. The overall gameplay doesn't change at all. There are some detail adjustments, but the general way a match develops is not gonna change.