Whatever you choose, I recommend you avoid using the PS3's built-in backup/restore utility with an external HDD. When I did a HDD upgrade on my PS3, I ran into numerous file corruption errors causing the restore to fail each time, and considering each attempt took 12 hours or more, I was just losing time and increasing my frustration. Eventually I just gave up and redownloaded everything from PSN.
The only "safe" method is using the PS3-to-PS3 transfer which utilizes an ethernet cable. That worked for me on the first attempt and completed about 150gb of data in under an hour.