I trained solely on slayer for pretty much all of my strength..... But i know alot of people use Yaks, rock crabs, and soul wars. Really depends on you tho.
Thanks for the responses, and I'm not really a big fan of slayer.. probably because I haven't really given it a chance. But yeah I was planning on botting most of the levels so I'm not sure if Slayer would work for that.
Stronghold of security is always a good place to train. But if it does get a little dull, I recommend you try out Armoured Zombies. They require partial completion of Curse of Arrav to get to, but being undead, salve amulet is very useful. Also, up a ladder only a few steps away is an altar to recharge prayer for more bonuses. Very useful for dealing high hits frequently and getting lots of experience. I can manage to get around 65-75k xp per hour at Armoured Zombies, and only 50-60k per hour in stronghold.