Do you plan on using the Shangri-La only as a tarp? or will you be using it with the nest?
Do you hate bugs?
Do you mind dealing with a bit of condensation?
If you plan on using the SL2 with the inner net, then the DR is lighter.
The SL2 with the inner tent will deal with condensation better than the DR.
The DR is bug proof, the SL2 is as well, but only with the nest
Can't speak for the SL2, but the DR withstands winds pretty well.
SL2 appears to handle snow loads better than the DR due to its shape, but this should be a minor concern for you since you don't plan on many winter trips.
Not having to deal with poles inside the tent is a plus for the DR.
SL2 is way more affordable, especially with the additional 20% couple at golite.com
I personally own a DR and love it. Good luck!