I prefer the C8/C7 series based on my operational experience. I have not wanted with it and it gets the job done. Remember, in the army, we all work together and have a system of systems approach to the use of firearms. When we go out to do the business, we have a bunch of weapons that can be applied to the task at hand. Some people say that the ### rifle is better or ### caliber is best....well I don't worry so much about that as I have a 25mm cannon close at hand and a radio which gives me access to B52s! For the firearm romantic, they envision a one on one type engagement and simplify the comparison in this manner. To be honest, the taliban can have the most accurate and reliable AKs on the planet....but I will happily apply a health dose of 25mm and 155 HE to overcome this. We have 7.62mm machine guns, 84mm rockets and a host of other weapons in my tool box. So for urban operations, at night, the C8 with PEQ2/PAC4 and NVGs, you can effectively fight at night in close terrain. If a target presents at long ranges, I have other weapons to deal with it. We can dominate the battlefield. Despite a lot of internet and gunrag gossip, engagement ranges are either quite close ie rock throwing distance or long range...with seldom in between. So if you look at thinks, we have the right mix of systems.
Now if you insist on an "Omega Man" scenario to base a comparison, heck I might have a different choice....but that is not my case. I fight taliban not zombies...and I do it in teams with a mix of firearms and weapons. So I hope that this clarifies things a bit. The AR15 system is good to go particularly for urban operations with the C8/M4 style. If the army needs more, we have the bits to cover off. If zombies are an issue for you and you anticipate being by yourself....well you might make different choices. As I once said, the operator is the important issue here not the caliber or type of firearm. Our troops are extremely well trained....
Jeff