One thing that can be said about the M4 is that it is combat proven. Back when I was hearing about all of the positive hype about the XM8 I asked my BiL who was in DF at the time about it and he said he heard the testing wasn't going very well. I'm pretty confident that the manufacturers that are wanting the contract are pushing most of the hype.

I'm happier that the different branches are spending money putting combat optics on the rifles than changing to yet another rifle.