Winch
I do not view lockers as a recovery item. Some times you can get high centered or worse off line. A winch will help you recover your vehicle from an unfortunate situation.
An example. This past October I was driving up in the mountains on a well cared for dirt road. No big deal right? I wasn't off road yet. Well It happened to snow the week before. I had no problem going through the powder snow but then the road turned to an incline turning road. Well with snow packed tires ( off road Mickey's), incline, turning road just made the vehicle drive straight. I got into a position that if it kept going straight then I would go right off the side and down the hill. I couldn't go backwards and I couldnt go forwards as the vehicle would just track straight no matter if the wheels were turned ( snow was fresh) and worse yet slide even more towards the edge. Luckily I had a winch and just winched my self around and out of the incline portion of the road until the road was straight and level.
The point to ask yourself. Is your plan to recover your vehicle? Then get a winch. Are you losing traction? get a locker.
I have gotten out of three bad situations with a winch in both snow, sand, and mud.
Cheers,