Up front I'll admit that I don't own either of these two shelters (yet) so my opinion is just based on reading BPL and other reviews.
I've pondered this concept as well. I'm 6'3" so a normal single pole Hexamid/Duo mid is a little short for me. It seems that I'm stuck with a variety of two pole designs unless I commit to the Megalight, Supermid, Trailstar, or Hexamid Long.
Even if there was a two pole Duomid offering, I would still have to deal with precipitation entering my shelter whenever the door is opened.
The SL2, Betalight, etc seem to accommodate my height better but when sharing the shelter, getting in and out seems to be more cumbersome.
I've pondered making a mock one out of cotton just to see if the design would work before trying it with silnylon. Figure I could disassemble it and use the cotton pieces as a template.
If someone would just offer a 5 oz double wall tent with an integrated hair jell dispenser it would really make my life so much easier.