If I was serious about the duplex, I would likely get the triplex. It is only a 3.5oz and $100 penalty but you can put two people in it plus gear. The duplex is only 45" wide. If two people each have a 20" pads, you have almost no room for gear. If one has a 25" mattress/pad, then no space for gear. If both use 25" pads, then one of you is out of luck with the duplex.

If you never plan to have a roommate, the duplex would be find. Never say never.