Played loads of PES 2009. Loving 2010. I would never go back, simply for one reason alone...
The ridiculous 90 degree turns. So glad their gone.
As for 2010, I don't find responsiveness to be an issue at all. I think the goals are much more random and varied than in 09 by far, mostly because you can't dribble through the whole team, and also I think Master League in 2010 alone is such a huge improvement that going back is surely going to be a mistake. Trust me, think about it, you might end up having to trade in 09 for 2010 again in a month, because it sounds to me like you just need to give the game more time to grow on you (i.e. for you to get better at it).
When it comes down to it, what PES 2010 has that maybe no other footy game ever has had is a certain degree of realism that comes not form the on-the-pitch play, but from the general uncertainty you have when playing it. Honestly, this might change, but I'm still never sure if I will win or not when I start a match, whereas in 09 I always knew that if I did certain things (dribbling through the whole team and shooting in close basically) that I would win.
Also, refs don't bother me, and although it could be said that the goalkeeprs are worse in certain situations, all in all with the better defending it's much better that 09 IMO.