I find the hunter pets much more survivable.
I think the warlock pets wear cloth while the hunter pets wear mail. at least that's they way it feels to me.
the hunter pets can be trained to be resistant to spell dmg and can be trained to have more armor or stamina, there are no (or few) equivalent skills you can train a warlock pet for.
The hunter can cast a pet healing spell that heals the pet over time and cures many things while the warlock must stop what he's doing and channel the healing over time at a cost to the warlock.

I like both classes, anything with a pet is fun but I find the hunter pets are better... imo.