My thoughts:
QBZ-191's focus on user end feedback is fantastic. Small arms design is extremely detail orientated. Well made and poorly designed service rifles all can all kill people efficiently, most of the times the guns are more accurate and reliable than the user. User experiences with how the gun handles makes all the difference. QBZ-191 has made significant improvements in this area.
Obvious features like the top rail, adjustable buttstock, modular handguard can drastically improve user experience. Other changes are less obvious. QBZ-191 has a grip storage compartment, which is great at storing batteries (you can never go wrong with having extra storage space on your gun). A better and crisper trigger can significantly improve the accuracy of the weapon. 30 degree angle of rotation for each fire mode on the fire selector switch means that soldiers can switch from safe to fire in an instant, which can be life saving in CQB.
AK style magazines are a pain in the ass the reload. I have yet to see a single person (with little experience with firearm) that can successfully reload a AK style magazine on first try, the paddle release on AK style weapons are often incredibly stiff, and inserting the magazine and clip it in is also a difficult process, even for experienced users. AR-15 style weapons are just so much easier to reload than AKs because of the way magazines are locked-in. The fact that QBZ-191 has a pronounced magwell, and an easy to release paddle means that the designers are aware of the problem of AK style flap release, and have significantly improved this problem for the weapon.
Center of balance on small arms is also important, especially for traditional layout weapons. I have a love-hate relationship with bullpups. One the one hand, bullpups are so much easier to handle since the front end of the gun is not heavy, but they have mushy triggers, and are incredibly awkward to reload when you wear plate carriers. Although traditional layout rifles have better reloads and better triggers, some are too front heavy. Front heavy guns are incredibly difficult to maneuver with. Hold down your aim steadily while standing up for more than 30 seconds can be impossible if the gun is too front heavy. For CQB operations where you need to open up a lot of doors, and handle our gun single handedly, a front heavy gun will exhaust you very quickly. The fact that users of QBZ-191 are happy with its balance, especially when switching from a bullpup to traditional layout, is an incredible achievement.
