This all depends on how you plan to use the truck... . if your truck is going to be strictly used for road use and towing you would probably be fine with a good after market limited slip (no hassle, no switch flipping, etc. )
However if you are going to be towing a heavy boat out of boat ramps, or taking your truck into fields to haul hay where there might be mud, or any kind of wheeling that might require a fully locked axle, then a locker might be a good bet,,,,
Detroit makes the best full time locker, but as stated there is a little chirping around corners, etc. if you take corners quickly, but since most of our trucks aren't sports cars, that shouldn't be an issue most of the time...
detroit also make a soft locker as mentioned above that gives better streetability, that an option...
ARB's are good lockers, but I personally am wary of them because first off it take a really skilled tech to install one properly, the differential has to be drilled for the airline to enter, the copper airline has to be installed properly in the diff, and then you have airline that runs back to your compressor to activate and de-activate the locker... . to me, just too many things to go wrong
Ox Locker makes a cable actuated locker that requires no special drilling etc, their system is built into their very heavy duty diff cover and a heavy duty cable runs into the cab, and you shift into lock mode when you need it... . only issue, is that I don't know if they make them for any diffs bigger than the dana 60 yet...
Then there are other brands out there that are pretty good, but not as popular as the ones listed above... lock right, eaton, etc. this doesn't mean that these are bad lockers ( I have lock rights in my Jeep), they just aren't as popular as the big three...
First step is to decide what you will do with the truck and the next step is to decide how much you want to spend and the last step is to take into consideration whether you are planning on a gear change, you will need to take this into consideration, because there may be different carriers for the lower gears, and that will mean a different locker, if you decide to change in the future. .
anyway, just a few thoughts,