Whichever recovery you have installed.
4EXT is the most popular here but a lot of people still use Clockwork Mod recovery.
If you don't plan to use recovery a lot then just stick to what you have. If you do flash a lot, like a lot of the people here, then you might like to use 4EXT touch for a nicer interface. Either way, it doesn't make a difference, both will end up achieving the same result.
If you haven't got a recovery installed all you have to do is download either ROM Manager or 4EXT Recovery Updater, install the app and flash the recovery. You probably know this though!
Anyway 4EXT can be found here:
The paid version is available in the play store and CWM can be found in ROM manager from the play store.