37f: unless you find a leftover 2010, you will find only Ford chassis under a new coach. Winnebago used the last of the big WCC chassis during their 2010 model year. The biggest dirrerence is that the WCC powered coaches will have a GM V-8 and ALLISON 6 speed tranny, while the Ford chassis will be a V-10 and 5 speed Ford "torqueshift" tranny. Obviously, I prefer the WCC power and that is "why" we pulled the trigger when we could still get the 37F on one of the last of the WCC W-24.
As long as you don't overload the chassis GVWR (24,000 lbs) you will be "legal" towing 5,000 pounds because both brands offer a 30,000 GCVWR. IMO, neither is going to be a rocket ship towing in "the rockies", but both can do it satisfactorily if you drive with reasonable expectations. Keeping the RPMs in the optimal power range thru downshifting will take you up most any highway grade.
The 2011 37F has a larger rectangular shower, which I think is an improvement over the slightly smaller curved door shower in ours. And our basement A/C was replaced with 2 roof mounted units in the 2011 models. I think other than those two "major" differences, the two model years appear to be the same , except for the chassis and color choices, which are also different between Adventurer and Sun Cruiser.
Good luck in your search!
Ed