I've always played on regular - This year it has become ridiculously easy but it makes for the a more measured and realistic way of playing. I find in professional/top player the CPU isn't that much better at attacking at all. All that suddenly happens is the implementation of AI tricks/cheating/manipulation ... suddenly the CPU players are stronger/faster making for a pinball fest and an unrealistic game.
This cheating makes the game very generic from my perspective as teams like Hull, Woves, Bolton play no different to Arsenal, Barca etc. I really hate this. Infact the AI/CPU is of a disappointingly low standard. Bolton, Blackburn, Stoke etc should player a long ball game whilst Arsenal should a quicker, free flowing game.
All the teams feel the same as it is on regular but professional/Top Player make it worse. I found the CPU attacks were better in the demo.