I actually really like the Cav Arms C6 "M4" style hand guards, personally. Honestly the initial reason I got them was that I really liked the way they looked in the pictures that USMC03 posted.
After trying both versions, I've found it's more comfortable to me to use the straighter hand guard with a thumbs forward grip than the tapered version is. It would also line up the light a little better with the bore line if you used a hand guard mounted 1913 rail, not that it really matters.

