Questioning Gas Power/Torque vs Diesel

If getting a Sprinter, regardless of model, I'd recommend a transmission cooler. T1N models don't need to have hoses cut into. NCV3 models will need to have hoses cut for the install process.

As for gasser versus diesel, this is fairly often debated, and some strong opinions on both sides. Diesels tend to be turbocharged, which means that they don't lose as much power at higher elevations, although the Transit will change that with the EB engine when it comes out later this year.

We bought our Era in Forest City, IA. After touring and putting the required 1K miles on it we pulled our Suzuki GV from Forest City, IA to Santa Fe, NM. The Era had no trouble pulling the Suzuki but it did seem to knock a few mpgs off the mileage. The only time I really noticed the Suzuki behind me was when I hit some bumps. It would yank on our Era pretty hard. It is pretty flat between Iowa and New Mexico so I can't really say how it tows in the mountains. We don't tow with the Era. The Era is a pleasure to drive in the mountains of northern New Mexico and Colorado. The Durango-Silverton-Ouray route was particularly beautiful in the Era. I am sold on diesel. I pass people going up long hills. They pass me when we go downhill.

For the OP, in case you didn't know it, all Sprinters of any of the 3 brands, Dodge, MB or Freightliner are the same vehicle, all manufactured by Mercedes. Only differences will be grilles, steering wheel horn covers and of course the badging.
We've owned 2 Sprinter RV's now, a class C & a B, 2009 & '13. We have had no issues at all in the mountains with pulling the grade. You learn to manually shift to 3rd gear and cruise up at 40 to 45 mph with the ability to pass, the Ford especially, class C's you come upon with no effort or strain. We've never pulled a toad with either RV not seeing the need to as we usually don't sit in any one spot for more than a day or 2, and both of the Sprinters would fit anywhere we ever took them.
Recommendation is if you want a Sprinter class B, to look for a 2005 or '06 chassis, or a 2008 on up chassis class B. The '05 & '06 would be on the T1N Sprinter, which is the original one that was sold here, least complicated with a bulletproof and non-troublesome 5cyl engine. Only issue with the T1N is rust & the turbo resonator which is an easy fix.
The NCV3 Sprinter is the 2007 on up model. Recommend staying away from the 2007 chassis, as it's had it's share of service bulletins and recalls. The 2008 on up ones have issues with emissions equipment which gets more complicated as the years go on. Their biggest issue is the EGR valve which gets clogged up from too much idling and just plain letting the engine lug around. Also the Diesel Particulate Filter which clogs up faster the more you idle and drive at lower RPM's. The V6 engine itself is bulletproof and a model of smoothness.
The biggest Sprinter issue though is lack of service facilities. They are sometimes hundreds of miles apart. And just because the dealer says Mercedes or Freightliner, doesn't mean they service Sprinters. For instance, we live in a metro area with a population of 1 million, and only have 2 Sprinter servicing dealers, one MB and one Freightliner. Neither one of these currently can do front end alignments on Sprinters unless things have changed in the last 90 days.
Hope this helps you

With a Mercedes diesel if you are not pulling a Toad you should be fine. I've spoken with a number of Sprinter (MB), owners and consistently their only complaint is the lack of torque which contributes to poor performance towing in the mountains.

Reports of 35 to 45 with the flashers on going up long 6% grades pulling their toads does not sound liked much fun to me. We don't have (need or want), a toad but should that ever change the V-10 will have no issues. As always.... Opinions and YMMV. :C