Do you mind having a temporary hack (where you need to run a hack program after each time you shut the PSP fully off), or do you want a permanent hack?

 

If you're experimenting with things and your PSP locks up a lot, it adds up.

The perm also has the ability to disable both gameboot and the intro splash, saving even more time on initial startup.

 

I personally use 6.20 Pro-B4 and I love it. however, if you are new to hacking I would say go with 6.35 Pro-B3/4 (for simplicity sake, since you won't have to downgrade)

Maybe play around with the 6.35 LCFW's and once you are in your comfort zone, then perhaps you could try 6.20 CFWs, who knows though, you might love the 6.35 LCFW's and may not even want to change.