Mike mikefarb,
My opinion only here.
I feel there are thresholds with motor home lengths. Generally speaking, if the rig can't fit in a normal single car parking spot, you crossed the worst threshold. That dimension is around 21 feet and a few inches. Then when you hit 25 feet, you enter another area of limitation, though less impactful.
Width and wheel base can play a role as well. For example, our rig is 23'-8" getting close to that next threshold, but our exterior width is a narrow 93" and our wheel base is a short 158" which both help with maneuverability. We do need two end-to-end parking spaces but we can move around in parking lots fairly easy. If we get lucky with the right kind of single parking spot, we can back in to an end spot with our rear over hanging the grass or whatever. Then we still fit a one-car space.
We've taken our rig on a 4 week trip last year out west, leaving our tow vehicle home and found that our rig presented only a few incidental limitations.
I feel the length of the rig is a consideration depending on the places you plan to travel to. For example, I would never want to tour a large city in our rig. We would tow our Liberty to leave the motor home at base camp, or even resort to public transportation depending on the city.
When it comes to the national parks and such, we appreciate the tow vehicle for maximum flexibility. Our Jeep Liberty 4x4 provides the ability to take unimproved and worse roads that a normal vehicle should not be driven on, let alone a motor home. Nothing is worse than travelling around the country to see all it has to offer, but missing out because we can't take those roads to scenic destinations and certain trail heads. Another consideration is being too large to pull over to see wild life and the smaller scenic over-looks.
If we were the kind of people who spent most time in RV parks, then length won't matter, but a tow vehicle would surely be handy for day excursions.