The 5 speed auto is pretty good. It has decent gearing so you can crawl in 4LO well for a stock rig.
You don't have to use DAC unless you want to turn it on. DAC is very good, you can really inch your way downhill w/ it- obviously no replacement for gears but you can also turn it off so it's just an extra feature.
The 5spd is super smooth so I don't see any drawback to it. It also has Toyota's lifetime fluid (no dipstick, no changes scheduled). I don't know if this is good or not- you can still change the fluid, the plugs are there.
The 6spd manual is very tempting but, for me, this is one more distraction while offroading. I would rather have auto and concentrate on my line- more skilled drivers may prefer the additional control a manual offers.