If you've played either past PoP game there is no reason to play this one.
Luckily, Prince of Persia Two Throne's has done away with this unneeded violence and gore and has more of a style closer to that of the Prince of Persia that appeared back in 2003. But on the negative side, the series hasn't progressed at all over the years. Whether it's graphics, sound, or gameplay, it's pretty much exactly what has been in the past games only with a couple of new additions here and there.
The big gimmick of Two Thrones is that there are two Princes, a good one and an evil one. The evil prince plays quite a bit different in combat than the good prince. As the evil, dark one you get a different weapon, are stronger, and just in general can be a lot more aggressive.
Then the good prince plays pretty much exactly how you remember he did in the last PoP game. There are a lots of moves and the combat is as fluid as ever, but to be honest I prefer the combat in the Sands of Time much more than I did in Warrior Within and Two Thrones. It took much more finesse and IMO was just more fun all around. That's not to say the combat in Two Thrones isn't fun, it's just not as fun as the Sands of Time.
A new move that the prince can pull off that is both very fun and very satisfying to pull off are the new stealth moves. You can perform ones in midair (which are particularly cool looking), but then there are others that you can perform by sneaking up behind enemies and with timing a couple button presses correctly, you can descretely take out an entire room of enemies if you can manage it. It adds a bit more variety to the combat, gives you some different options, but I would have liked to see a few more animations for these stealth kills.
But even with some new additions here and there, the game for the most part plays exactly like its past incarnations. The same combat, the same acrobatic puzzles, etc. It's still as fun as ever, but the game has just become REALLY stale over the years.
This might be able to be overlooked if the game at least looked different. But unfortunately that's not the case. The developers have been using the same graphics engine for the past three years and it shows. What was once an impressive showcase for the current gen consoles is now showing it's age quite a bit. Lo-res textures, blocky characters, etc. It just doesn't compare by today's standards especially with so many other better looking games out these days. Some of the lighting is still great and the animations are as impressive as they were two,three years ago.
Prince of Persia Two Thrones is a really good game. It has a commendable score, story, and puzzles, but this series has gotten stale very quickly over the past three years. Instead of just trying to quickly throw together a new PoP game every year just for the sake of making money, Ubisoft needs to just let the game's developers take their time and move the series forward again and feel just as fresh as it did when it was brought back in 2003. Since all of the PoP games play very similiarly I really think you'd be best off picking up Sands of Time isntead. All of the PoP games are really good, but Sands of Time is not only the cheapest but also probably the most value packed out of the bunch too. But if you have played the past two games, love them to death, there's no reason why you shouldn't check this game out.