I got mine for $39.99 from Kmart last week and it came with a free UFC t-shirt. (I was all pumped after UFC 116... the greatest complete MMA card ever.)
Then I went to WORK.
First I downloaded the demos for both games. Then I went to Gamestop and bought 2009 for $19.95 knowing that if I didn't like it I could just return it, but figuring if I *did* like it enough... then there was no point in keeping 2010.
2009 is a very fun game and there is a lot to like about it. (You have a wrestler? Somebody throws a kick? Attempt a takedown and you'll grab that leg and toss them to the ground. And, while you're on top and they're holding onto you, you can pick them up and slam them to the mat Rampage Jackson style.) But the presentation is EXTREMELY lacking compared to 2010. Add to that basically every fighter is the same. You're either a wrestler or a brazilian jiu-jitsu guy. So Chris Leben fights just like Shogun Rua. And Chuck Liddel fights just like Rampage Jackson... which is stupid.
They changed all that with 2010. I was absolutely DELIGHTED to find you could use Chris Leben exactly like he performed in UFC 116. (Opponent takes you down you can rubber guard him and put him in a triangle choke like Leben did to Akiyama.) There's a lot more variety, twice as many submissions, and everybody complains about career mode but I've really enjoyed it. I learned a lot about the game that I didn't know before... even after about a hundred hours of research into both games (for example, that if somebody had *you* in a body clinch you could JUDO TOSS THEIR ASSES!)
I've only played a couple of online games and while there was some lag it was an acceptable amount. I could still pull off whatever transitions, submissions I as trying to do. My punches still landed when I wanted them to land and countered when I needed them to counter... so I'm not crying over that.
I do wish you could catch somebody's leg like in 2009 though... You can do it in 2010, but you'd have to do it manually. (Kind of reminds me of how in Smackdown Shut Your Mouth Kurt Angle could catch your kick and reverse it into the Ankle Lock using just a button or two but in the next game, Here Comes the Pain, there was this whole complicated way you had to do it.)
I've been playing fighting games and wrestling games for as long as they have existed and I must say... for only a game's second year... they did a decent job with 2010.
The presentation HAD to be upgraded. And they did. The music in 2009 SUCKED. And they replaced it. They added more moves and more fighters and the PS3 version comes with Bluray versions of some classic fights.
And I got a t-shirt.