Look at as many floor plans as you can, in person. Move the slides in and out. Move from the cockpit to the living area and get a true feel for the vehicle. Take it for a good long test drive.
Do a lot of reading on the Ford and Chevy platforms. The Chevy is preferred by many but obviously the Ford outsells the Chevy, I believe primarily because of price. There are many Ford owners on this forum who like their rig. Read reviews and do a lot of study.
We have a 24 foot Sprinter by Thor. We like it, plenty of living space with the slides out. No slides and it would not work for us. We travel long distances in a short amount of time. Its been a very good rig for us.
Good Luck!
Rick