I had both these campers in mind for fulltiming too ... if you are driven to make the "right" choice for you, you really will need to see them in person. Photo's are nice, but nothing like getting a sense of the materials used, experience the colors, how the space works for you, the kitchen, etc.
One of these campers is likely to be "it" as soon as you walk into it.
Looking at pictures, I was always wondering which camper I really liked better. As soon as I walked into the 1165, I thought that was it. Spent a number of hours in a Mammoth, Everst, 1165 and 1200 in a couple of RV shows and at dealers, my intial impression after actually looking at these campers didn't change.
I don't see many used ones of either mfg ...
Enjoy and good luck! Most people say buy the floorplan you like??
I"m looking to fulltime as well, and now also thinking about Northstar 12 STC . I'm single, so should be able to fit!