My preference is manual locking hubs, have heard too many horror stories of somebody out 4 wheeling going downhill, and using the engine as part of braking via the load placed on it from all the wheels being locked in (mainly manual transmission, of course) and the auto hubs disengaged because there was no forward load on them from the drivetrain.
Under certain conditions, I can see auto might be convenient, but I still like the dependability of manual.
Warn are the best, mile marker is a little less costly, and I have personal experience with them, no complaints, they paid for themselves.
EDIT: I probably should have mentioned for those on the site that don't know me, I live remote in the mountains and off the grid.
To get to a paved road, it's almost six miles of HORRIBLE roads, zero maintenance, lots of traffic, and after a storm the mud will swallow a car whole.
MANY 4x4's get stuck here.