In my truck, the rear elocker just makes things worse in 2wd. In 4wd it's priceless. I'd invest in these first:
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OEM e lockers are very reliable.
Arb and Yukon Zipp air lockers are very reliable.
Yukon Grizz and Detroit Lockers are the most reliable.
Eaton E lockers are less reliable but still good. Depending on which type of axle. Some homework is required here.
Auburns ECTD locking LSD has been improved and may be a nice option. It'll required LSD type maintenance.
Detroit Truetrac LSD is very popular still, and perfectly reliable. A good option if you're keeping all four tires on the ground.
If you live in an arid climate, I'd put in the Yukon Grizz autolocker.