I don't want to hurt anyone's feelings here but a Sprinter is old hat and old technology compared to the Transit. Ford waited years to design and release this new chassis, so every other van out there is dated when comparing, speed, handling, brakes, comfort, etc.
Engine - The Ford Power-stroke diesel engine is bullet-proof and makes more power and is twice as responsive as Mercedes dated V6. After you drive the Transit with a load and feel the power and handling, its tough to climb back in the Sprinter.
Transmission - The Transit's 6 speed with its "Trailer Haul" feature for spreading the gears and downshifting to save the service brake, is light years ahead of the "Decade Old" dated Benz 5 speed, which should have been dumped years ago.
Cab - The Sprinter cab and dash is old style work-truck styling compared to the Transit. The Transit is modern with easy to reach controls. The AC vents are actually there where you need them. The shifter is only inches from the wheel, so there's no looking down to find it. In fact, the sprinter shifter is so low I use my knee to up shift. The transit transmission has two different manual controls one right on the shifter knob.
Suspension - On a Sprinter you feel every single road imperfection which transmits right to the cab. The rear axle transmits bone jarring shock to the rear which can dismantle cabinets. The Transit is smooth and quiet, you don't feel every bridge and there is no transfer of shock from the rear axle.
Handling - Most important is the handling, the Transit has 50% less roll moment than the Sprinter thanks to an improved suspension system. In addition, the Transit uses a low CG chasis style with low profile tires there is no sidewall flex increasing roll moment.
Service - I won't even begin to bring up the thousands of reasons you would prefer to have a Ford over a Mercedes when it comes to finding a dealer. If you break down, pray that it happens in a major city. If you happen to find a Benz dealer, you better catch a flight home or find an "Extended Stay Motel" because their dealers all suck and hate van owners. On the other hand, you can take your Transit to almost any Ford dealer and get service in a reasonable period of time.
After Warranty - After your Sprinter warranty expires - get yourself a real good "Home Equity" account, because you'll need it for any repair. Mercedes does not count in dollars, everything is hundreds and thousands.
Just my 2 cents!
Enjoy - Mike