Before saying anything about performance read these!
http://www.eurogamer.net/articles/digitalfoundry-ps3-hard-drive-upgrade-guide
7200RPM makes it a tiny bit faster
http://www.eurogamer.net/articles/digitalfoundry-can-ssd-upgrades-boost-ps3-performance
SSD is not worth it.
Well maybe if you only play GT5
I swapped my 320GB to a 750GB.
I bought this
http://www.amazon.com/dp/B004I9J5OG/?tag=neogaf0e-20
7200RPM and more cache makes the system a bit faster, but if its space you need get the 1TB. That was not avilable when I got mine.
Also its not 1TB its 900GB something due to how its calculated and the PS3 OS is going to reserve a certain ammount of space.
For excample my 750GB drive had 600-ishGB space left when booting up for the first time.
1. Delete all game/install data, you can install it again later
2. Run backup utility, took a few hours for me, saves almost everything, even Users and PSN logins
3. Insert new HDD, just find guides on youtube for the type of PS3 you have. It can be a bit tricky I thought and Im used to hardware
4. Get a USB stick with the latest FW update. Folders PS3 -> UPDATE
http://us.playstation.com/support/systemupdates/ps3/pc_update/index.htm
5. Plug in USB, turn on system, follow instructions
6. Run backuputility
7. Install the games again
Enjoy!