My prospective is somewhat limited since I have only owned 2 Montana fivers, one used and now one new. However, I never was a part time RVer, we started right off as full timers.
The first unit was a 2008 3400RL. Very well taken care of and nothing ever needed fixing while I owned it. The present unit is what is in my signature.
We compared 3 or 4 other brands before purchasing the new unit. We honestly thought that the interior was better in the Montana, plus some of the other options we liked for full timing.
It has served us pretty well. We purchased from the biggest dealer in the nation. Problem is we travel all year so it was hard to get back to the selling dealer more than once a year. The things that did need fixing were certainly a struggle getting fixed at other dealers. IMHO the factory doesn't honor their 1 years warranty all that good also.
Fit and finish, and if you are actually going to pull the thing down the road for 10,000 miles or more a year than you probably can't go wrong with the Montana. I would shop for an extended protection plan though.