In HC the M8 is often a one burst kill. So it's great there but in Core its not the best. I'd say the AN is better for Core.
I want to say the AR's are the best but for myself I tend to do better with smg's... however! I refuse to use them and stick to the AR's mostly.
I prefer the scar at the moment.
SMG's for me were my first diamond gun, then again i cant stand single shot Assualt Rifles....Meh. SMG's for me all the way but they keep changing them, MP7 has insane recoil now.... ugh
I play core and I run and gun tactfully. I can dominate on any map with an AR but it has to have a stock on it. I dont even touch SMGs anymore. When the game first came out my opinion was the opposite though.
Yeah since a couple of patches, AR has a slight edge. Well some specific AR, AN-94, M27, SCAR-H, (SWAT when long range is involved for sure). But you are pretty much required to always use stock, i think alot of people not liking AR or not using them to run and gun simply dont use stock, not having stock on an AR is such a huge weakness its pretty ridiculous sometimes. When it comes down to it, AR have the kill speed advantages even some at CQC ranges. The most consitant SMGs dont have kill speed close to ARs at any range.
I got both AR and SMG diamond, im more likelly to pick AN-97, M27 above any SMG and im 100% a rusher, no ghost, pretty much tac mask and flakjacket on every possible setup lol, my KD with both guns is around 2.50+ last time i checked.
I think the Type 25 is one of the best guns overall as it really is like the best of both SMGs and ARs rolled into one. It's got the ranged power and moderate recoil of an AR combined with the fire rate of an SMG. Slap a laser sight and stock on it and you'll actually beat most SMGs up close while remaining competitive with ARs at a distance.