Here's My View...
From all the posts and comments I've read in the DIAS vs. RR debate here's what I've learned :
- a RR is more expensive because all the component parts to fire full auto are contained in that one package. Nothing needs to be swapped or changed, just pick up the rifle and go. With a DIAS you have to supply the upper and lower, component F/A parts and insure all fit and work together.
- some RRs are more valuable than others because they are considered more collectible, e.g. a Colt RR is more expensive than a Sendra, though both may in fact shoot the same. There is no collector status for DIASs.
- with a DIAS there may be some fitting needed to make it work in a specific gun, issues regarding fit and timing. However, you DO NOT want to make any changes to the DIAS - any changes should be made to the host gun only. If you alter the DIAS, you may alter it to fit one gun but it may not work in others, hence you lose any "swapping" advantage.
- if you move the DIAS from one gun to another, the gun that no longer has the DIAS must also no longer have any F/A parts; if the gun is a post-ban then any pre-ban features installed while the DIAS was in use must be removed. Also,there is no provision in BATF regulations to notify them that you are moving the DIAS from one gun to another.
- DIASs are generally considered pretty indestructible. And if it breaks, fixes by reputable Class 2 manufacturers are both cheap and simple, as it is a cheap and simple device. If you run a lot of rounds through a RR and it shows stress, it may need to be sent to a Class 2 manufacturer to attempt repair. With a DIAS, if a lower starts to show stress, you just buy a new lower.
I probably forgot a good point or two, but those are the highlights I recall.
If you already own an AR-15 and could care less whether you possess a RR or not, then a DIAS may be your best bet, as long as you remember there may be a degree of fitting involved. But if you want the je ne se qua that owning a RR brings, that may be your best choice.