The reason people consider the manuals an upgrade is that they don't disingauge when you slip back down a hill. Once they're locked, they're locked. Auto hubs are designed to disingauge when you roll back (part of the unlocking feature described on your sun-visor). Great when you don't want to get out of your truck in the mud and snow, bad when you're stuck on the side of a hill and have to get moving forward in 2wd to lock the hubs up again.
With manual hubs, always engage them before you need them, but keep it in 2wd unless the situation warrants. Keeps your boots clean.