I'm on the fence. Ford E350/E450s are good and time-tested. Sprinters get good gas mileage, are reported to handle better than the Fords, and have the M-B mystique about them. However, the cost difference between a Sprinter and a Ford chassis can buy a lot of gasoline.
My biggest critique with Sprinters is finding service. I live in Austin, which has an excellent Freightliner and M-B shop, so where I live, the parts are expensive, but I know where to go if I have to deal with a CEL or even worse, a LHM condition (Sprinters have multiple degrees of limp home modes), and the Scangauge II doesn't fix it.
Were I in another part of the US, service depots might be an issue. Sprinters require alternate "A" and "B" upkeep. One is supposed to drain and refill the DEF tank at those service intervals, or urea crystals might create problems down the road.
My second biggest critique are small items. I need another ignition key for my Ford, I can authorize one if I have two masters. The M-B has to go to the service station. I lose all my keys to a Ford, I attach a terminal, wait 10 minutes, and add two masters. The M-B goes to the garage, possibly to have a chunk of the computer replaced. Same with remotes. A Ford remote is cheap and easily added/removed. If I want a numeric keypad on a Ford, that is trivial to buy, stick on, and program. The Mercedes requires a fiddly one that sticks on the inside of the windshield, and I have no clue if it might work with the 2014 model.
Were I to have a Ford chassis, diesel emissions stuff isn't an issue, and the Ford V-10 is extremely reliable. My only possible gripe is probably having to find a good RV suspension shop to add (and install) aftermarket items to make it handle better, but that is subjective.
Another factor is the generator. You can get diesel generators, but usually a Sprinter based rig will use the LP gas. For some, this is fine. If you live in Texas where A/C is a must, it may not be enough run time.
If I had to choose between a Ford E-450 chassis versus a Sprinter chassis, I'd lean towards the Ford, assuming everything else is equal. The $10,000/$20,000 chassis cost difference is a lot of gas saved. Plus I get a lot more run time of a generator from a 56 gallon Ford gas tank than one running from a 26 gallon Sprinter tank.