Paring down to essentials...
One aspect of the X7 design was to trim back to fighting weight and eliminate needless bureaucracy.
Forend
Quad rails were thrown out to the great benefit of your forward grip. Instead, a lighter weight and more rigid handguard cage was provided that fits the hand better. The hand now can wrap entirely around it or nearly so, which means the muzzle shifts less around your intended POA.
On other grip systems, such as larger circumference quad rails or worse on vertical foregrips, there is less leverage in either x or y or often both, and so there is more play in the correspondence between your muzzle position and your hand. Besides, these other systems compound their disadvantages with extra (needless) weight out near the muzzle where it hurts.
The problem with this story is how to prove it. Several of our most expert testers have found split times to decrease 10% after some time training with the X7 and compared side by side with their fastest previous AR. Presenting this kind of comparison in a fair, scientific way is too difficult at this point so we simply leave it up to your analysis.
Controls
There was much internal debate about controls, especially about ambidextrous features.
We tested the most popular add-on ambidextrous mag release and liked it a lot. The problem was it was hotly rejected by several expert testers and there were a couple instances during testing when a magazine was dropped from the well due to the left button hitting something like a spare magazine on the tester's belt rig.
Ambidextrous safeties are easy to design. We rejected it right away in preliminary review because of an important, although admittedly not widely known, advantage of the old design. In the field, if a small object such as a pebble or loose primer gets hung up between the trigger bar and base of the lower receiver, you have to remove the trigger rapidly or at least release it somewhat. The easiest and fastest way is to punch the safety selector out from the right side (position the selector half way between fire and safe first). Hard to do with a right hand side lever in the way.
Ambidextrous bolt catch/releases have ranged from bolt-ons to integrated mechanisms. There are currently one or two nice implementations out there, but we haven't tested them and just didn't have time to fit into this project.
In summary, we did improve the safety selector and the mag catch but only by making already good designs better and not changing them radically.
In other words, we ended up concluding "simpler is better" when it comes to the X7's controls.