I stopped by a FR dealer, and if you want one of their rigs, it will be a blue oval. I wondered why no GMs, so I'm guessing the above -- more Colorados and Suburbans, fewer 4500 chassis. To me, does it matter? I'm used to Ford, but nothing wrong with Chevy/GMC.
As for Sprinters, this discussion has been hashed out a bit. The two biggest disadvantages for that chassis is the price (usually $10-25k above a Ford or Chevy), and the lack of repair places in a lot of areas.
As for Dodge, the older Sprinters, I'd lump in with Mercedes. The newer ProMasters are a different beast entirely. Downside of the ProMasters is their anemic cargo capacity, so they wind up being used for only light, slideless rigs like the Winnebago Trend.
Of course, don't forget the curveball that will be smacking the "C" industry in the face in several years. Ford should have the heavier duty (T-450, T-550) Transit based cutaways out in a year or two. These will replace the Econolines... but as far as I know, -nobody- knows what engine choices these models will have. Perhaps a diesel, maybe an EcoBoost... who knows.
As of now, I have looked at almost everything out there. Nothing against Sprinters, but I don't see anything it provides that the E-450 doesn't... the cost difference can buy a lot of gas, and the Ford V-10, once it is out of warranty, has a whole slew of aftermarket stuff that can be done with it.
I will say I've seen E-350/E-450 rigs in extremely sad shape. However, they start up and run even though the radiator is likely shot, the gas has water in it, the oil is sludge, and who knows what is passing through the air filter.
I do like the recent updates to the latest model Fords as well. Especially with 7500 pounds available on the hitch, which comes in handy.