I think what weapon you use depends a lot on your style of playing.
My style is usually to inflict as much damage as I can without getting caught or killed myself. That means I shoot far enough way to not be heard.
I use the M24 because it gives me the best distance and accuracy with the least sound. If I plan on shooting mostly from 800+ then I'll use the MCRT for its extra scope magnification, but I've gotten headshots and moving kills with the M24 from 1000+ meters.
Yeah, it takes longer to reload, but you should use that as your cue to duck and change positions.
