Installing a locker that requires the replacement of the carrier is a PITA unless you have the proper tools (Dial Indicator) and someone with you who has LOTS of experience. If you get the gear backlash wrong you will wear your gears out in a hurry and they will be noisy as hell. It can be done, but it's a pain. The big advantage of a standard locker is that you can unlock it and drive it as an open differential. The lunchbox lockers release in the corners, but they make noise and you occasionally get a little wheel chirp and a thump under the truck. They also add a little more backlash to the drivetrain.
Putting a lunchbox locker in is a piece of cake. Took me about 2 hours to put the No-Slip in my X. As for being not as strong as a standard locker, I have never heard of anyone breaking a Powertrax. After installing one and looking at how they are designed, you will bust an axle or a universal long before you bust the Powertrax. They are solid!
If ya go with the lunchbox locker, I can give ya a hand installing it if ya want.