I personally prefer BH because I always pk in it and even if you die with something valuable on you, you get to keep 1 item if you pk in the correct worlds. Also, because BH has more safe zones and multi-zone spots for pking with a friend or more.
If you're one of those players that are really generally new to PvP, I would just go to BH to start off with because you have that 1 person target limit you can worry about. When you don't have that person located, you could attack anyone else, but would have to wait until the expiration is over.
Bounty Hunter for sure, nothing like a target kill. PvP is way too spread out as far as levels go. I hate fighting someone with like 12 combat levels on me.
If you have a target BH is better as the drops are substantially more, PvP if you do not have a target because it is easier to find someone to fight (due to the level range)
At bounty hunter, you usually get more the armor of the dude you killed, than random things such as d baxe, mystic robes and farseer helms that you would get istead at pvp worlds.