Although the D&E gun is a much more scale replica, it is loaded with engineering problems. Very few people have gotten one to fire reliably. Even the D&E website shows pics of a gun with bolts that are NOT made to the prints. Also, be aware the D&E gun uses 22 shorts which are much harder to find and more expensive.
I completed a D&E build to about the 75% stage when I found out about all the design problems and non functioning. I ended up using the RGG internals design, scaled down with changes to the bolts and putting that into the D&E housing for a functioning gun.
As a result of my experience and a LOT of research, I would suggest building the RGG gun and copy the external cosmetic details from the D&E design, best of both worlds.