Have had both over the years - back to GM's Turbo Hydromatic of the '70's. Assuming a decent transmission, either will work.
-- Auto can be better in soft sand, but you can learn to manage the clutch with care. Some autos have a "snow" mode which starts in second to reduce the torque. Some swear by it, others simply modulate the accelerator.
-- Auto is less work in traffic - a real issue with my 917 and arthritic knees!
-- Autos can be prone to hunting a bit on roller coaster roads (think Andes back roads). That is, you climb a grade and the trans upshifts at the top, when you want it to stay in gear for the descent. Modern transmissions often have a sport mode or tow-haul mode which will eliminate this problem. (Isuzu in Bolivia had the sport and Chevrolet in the Rockies had the tow-haul.)
-- Almost any modern auto can be locked into either a single gear or lower range of gears for long descents.
-- A modern auto transmission can spare the drive line - no jerks in the drive train even with a jerk behind the wheel.
-- All require maintenance - fluid changes, clutch adjustment/replacement, etc. A temp gauge and knowledge of the temps for your transmission is nice for rough use.
I don't know about Mercedes Benz auto trans, but on the 917, with a lot of traffic and a transmission two meters behind the steering wheel, I often dream of the lovely six speed Allison on my Chevrolet. (Wouldn't mind the 800 foot pounds of torque, either.)
Hope this helps.