I've always found that people who actually use 4WD on a pickup regularly prefer manual locking hubs and people who use 4WD only rarely like the automatic/electric/vacuum locking hubs.

My beef with the electric/vacuum hubs is that when you need them after you've climbed through 1500' of elevation and slush in the Sierras and then you get into the "this is a serious snowstorm" conditions, automatic hubs will choose that moment to not work.

And, as always, it is just one more thing to fix on a rig.

Oh, and one more thing: some automatic hubs require forward or reverse travel of 10' or more to lock up. Let's say you're moving along on a back road out here and you get into a poof hole or mud waller and you're stuck in 2WD. Guess what? You can't get the rig to move to get the front hubs to lock in... unless you have manual hubs, in which case you get dirty, but the hubs engage and you might get out.