OP it depends on what you want... a locker is not "wayyy" better than a limited slip (or any traction aiding device).
If you want something to help get you "unstuck" once you have already become "stuck", a locker will be superior. Or if you plan on really driving through some rough terrain consistently at very low speeds, potentially better.
If you want something to help prevent you from getting stuck, and assist with take offs in low traction areas, the LSD is superior.
Everyone is always quick to spout off about lockers...but truth is they suck in most applications. Assuming your truck is 4wd, the LSD is most likely the way to go. Having both rear tires helping you prevent becoming stuck in 2wd will be a HUGE step up from an open diff. Especially in such a tank of a truck. And the moment you start to get stuck, you flip on 4hi, should be fine.
If you are really doing some hardcore offroad driving where you think you need 3 tires turning at all times, a locker will be better. But the truck wont turn as well, it will handle differently, and if you are on wet or icy surfaces, you better be careful and SLOW.
the bottom line is this:
a LSD is made to function 100% of the time, help with every driving condition, and prevent you from getting stuck.
A locker is made to be engaged, used briefly to overcome your obstacle, and disengaged. You are still driving around open diff 99% of the time.