Many years ago we wanted to upgrade from the popup too. We learned that there are many factors that determined our ability to safely tow the new camper. At the time, our tow vehicle was not a good match for what we wanted to buy :(.
Make sure you check out "VEHICLE LOADING INFORMATION" and "TOWING A TRAILER" sections in your Nissan owners manual before you purchase a trailer. I just want you to be confident in towing your new home away from home.
Now, with all the floor plans being similar, I would look at the appliances and other amenities that are important to you.
For example the hot water heater. Is it DSI or do you have to light the pilot. Flipping a switch is much easier than crawling around in the dark trying to light a water heater. Is it just gas or gas and electric?
Heat pump, gas heat, heat strips?
Microwave?
Storage Space (especially for long trips)
Enclosed underside (for cold weather camping)
Etc...
Happy Camper Hunting!