If you go with the Medium Duty like the UHaul's, its a 10qt sump and ALOT more forgiving of oil level. It might be a bit more intimidating for an employee-mobile, but that might be a good thing? They are surprisingly maneuverable, but you also never forget you are in a large vehicle. My 34' MH can cut a U turn on anything slightly larger than a residential street but I would never dare to try taking it through a fast food drive-thru. Easy to work on, oil changes are simple, everything is pretty accessible (especially on the gas engines). Allison transmission, pretty sure an Eaton rear end. Tires aren't the cheapest, and you will want to upgrade the front shocks and possibly sway bar, but otherwise a very solid, reliable setup.
BTW, don't believe the tow rating on the UHaul site that says 7500 lbs. That's probably just the bumper rating, using a legit hitch should get you 10k plus, and doing a 5th wheel/gooseneck is going to be on up there as well.