I've been sitting with this as well and the choice really is yours to make.

For benchmarks and extra info you might want to visit this link: *Click me*

Personally I have decided to switch from MySQL to PDO (instead of switching from MySQL to MySQLi) after reading a lot of different things on the web.
For me, the following points were the reason to go to PDO:
- MySQL will slowly go and PDO will be the new standard
- PDO is now standard in PHP and since it is pretty new, I'm convinced it will be improved
- If I need to change my database, it certainly will be easier with PDO and only a vew queries might have to be changed (since I use pretty standard queries)
- PDO is OOP and while it might not be a real argument for some people, I do like programming OOP above Procedural since a while now

*Some info I found may be false, if so, then I would like to hear this as well =]
- I like prepared statements above using mysql_real_escape_string() all the time