I lived in an 18 footer for a little over a year. Also used it in a mobile application for years afterward, using it to camp for 10 days at a time. The 18 footer contained all my worldly possessions at the time,including the dog, but not the pickup. Once you can get the set right, the lodge can be as comfortable as a house, even in winter.
One elk season the 18 footer slept 10 guys. There were six of us to begin with, then a camp nearby had a flat roofed tent that collapsed under a foot of heavy wet snow. About 2 AM there was a knock, and the guy asked, "Can we come in there and sleep with you guys?" With ten of us in there, it was a bit crowded, but we managed.
The year encampment was in the company of two other lodges, both 16 footers. Both were the abode of single ladies with all their possessions. One stayed there for three years, the other for two years. This version of suburbia was a picture to behold.
Whichever you buy, have fun with it. Don't let the internal fire get too high. One of my elk hunters built a huge fire and burned the liner, even though the liner was treated to withstand fire. After that, I used a small woodstove when having out of town guests.