I played with SMGs for a while until I unlocked a decent AR and then I stuck with that. I've found the ARs easier to use by and large (though with 'range' attached, SMGs can be pretty  lethal). Generally when I get bored with one I just switch. They're both much of a muchness in my opinion.

Depends on the map. On maps with lots of med-sized combat like Arkaden, Village or Lockdown an assault rifle is good, while on smaller maps or maps with a lot of CQC like Seatown or Hardhat use a SMG.

But I'm the kind of guy who likes using every weapon class in the game.  On larger, more open maps like Downturn or Interchange I find a good LMG to be good, while on maps with lots of hiding places (i.e. Fallen or Bakaara) use a sniper.  Then, I pull out a AA-12 or Striker on Dome and sometimes Hardhat.

Ars are still the easiest class to use, especially with so many headglitch spots, that extra range and less recoil helps a lot.

My favored smg is the pp90 silenced or with rf (overkill, but a lot of fun run-n-gunning), favored attachment is range, so I can burst fire mid range and hope to beat ars while pwning them cqb generally. Cheapest smg is the mp7 since it has nearly no recoil while dealing 20 damage long range, it's a hybrid smg / ar, very cheap to use imo.

Got to say Impressive moab Run-n-Gunning. Not even dropshotting, one on one. That would have made it better to watch though imo, just for the extra pwn effect.

Very nice. Im getting sick of domination moabs. Boring.

Pp90 is king to me silenced w range. But I can be successful with any class of weapon on the same map, really its about swishing up your routes/spots to maximize weapon and loadout efficiency.

Also it depends on game mode. In tdm I just can't seem to run smg in village (my one fail), but kc or dom smg can be beast.

If I want the top score tho, I always go smg with tactical insertion in the middle of the map lol.its not the greatest sometimes for your kdr tho but always at least positive!

Depends on the map I use SMGs for close range maps and I use assault rifles for open area maps

I use both AR and SMG. AR and light machine guns with larger mas like Interchange and SMGs for close encounter maps like Dome. Of course that in certain areas of all maps some might have more advanatge than others but this overall rule has worked ok for me.

As cheesy as it is I usually use 2 attachments silencer/thermal scope on the MK14. It's fantastic at holding objectives on DOM.

For KC, TD,  and Free for all I use the PP90m1 with range and rapid fire. This is fantastic when paired with specialist and scavanger as your first specialist perk. That way after you get a couple of kills you can start refilling your ammo which is getting low by then. I usually main spec Blind Eye/Quickdraw/Stalker for that build.