I personally prefer the Combat because it has a better damage output...although I'm masking it with the S3. Feels as strong as a M416 CQB unsuppressed.
If its far range, then you better learn to burst/tap with the M417 Combat, the bonus is that the non-existant side-to-side spread with the upward recoil gets me a lot of headshots, lol. It also has the faster reload, the SRT is like somewhere between the combat and the cqb, although I don't like a tan colored gun and costly since it doesn't have an integrated scope (yes...I'm perfectly fine using the iTech and the HDS-Reflex over the Acog/Triholo).
PS:
M417 SB > all other ARs