I have constructed denim quilts (both rag and regular) using both kinds of fabrics, and I enjoy the look and feel of it from a texture perspective. As long as the colors are complimentary and to your liking, I see no reason not to.
However, I think the biggest thing to consider here is the preference of the individual whom it is intended for, and perhaps that can sway your decision. Some people like to lay their hands on the quilts as they use them and are sensitive to texture and feel. Some people never touch the outside and are always under it - so they don't have a preference.
Also, on a relevant side note - I would mention that with the thicker denim on the GO! - (I have the same one and die) you will be able to cut less squares with thicker denim at a time, as the threads want to get caught up more in the die with that material (and that fact that it is a rag die to begin with), which you will have to religiously pick out in order to get clean cuts - no matter how new the die is. So I have found that as a result, it's just much better from the get go to cut thinner stacks of the thicker denim as it is less work and practically guarantees a clean cut every time IMO and minimal "threading" of the rag die.
Explosive blessings, abundance and inspiration to you all!
- The Creative Seamstress