Don’t guess. If you can load the Frontier will all you expect to be loaded in or on it and get it weighed with full fuel. Do the same with the mh when you get it. Not sure how much it weighs but we tow a 2015 Jeep Wrangler 2dr hard top with a few hundred pounds of stuff with our 2016 V10 six speed Newmar. Works great. Yes it will churn out 4K plus rpm’s when going up steep inclines, but it makes it up every time, passing most trucks. The V10 also does a great job going down the same inclines but down shifting. (Also can be a bit noisy).
And just to set expectation’s in the six years we’ve owned the thing, the V10 chassis as been wonderful, but has never seen a mpg number of 8 or above. Most 7’s sometimes 6.