No question about it, 40' motorhomes are nice - spacious, lots of features, etc. We drove 40' motorhomes for over 14 years and 185,000 miles. Recently we purchased a new motorhome that is a Newmar diesel and it is 34' long. I cannot get over how nimble it is, how sharply it turns and easy it is to maneuver. Both my wife and I have remarked also that we really don't feel any more crowded in this motorhome than we did the 40' motorhome we traded on it. The biggest thing we had to give up was the extra 1/2 bath, and we haven't suffered a lot from that. We still have our washer/dryer, and our 4 door Norcold refrigerator. So far we are very happy with the smaller coach.
I guess what I'm trying to say is that yes, in the northeast particularly, you will find state parks and other campgrounds that have limited space, if any, for 40' motorhomes. Also it is a lot easier maneuvering in tight spaces when you are driving in a shorter coach.
Ed