I prefer the '43 when i can get it, half the mag size, but you get more mags, making ammunition management easier. When you only have 3 mags and a smart-mag system like RO has that monitors the number of rounds left, i don't want to end up reloading, have the mag read as heavy and then only get half the clip. Also the '43 is more accurate i find, especially when rested.
No '43 and i take the '40, it's not too bad for accuracy upto about 250-300m, so long as you take your time and fire bursts, even if you're not rested it's still reasonably accurate, plus a lower ROF is always a good thing in my book, i want to kill, not pepper, and when i kill i don't want to waste rounds i could use to kill other people.
I usually try to avoid the '41, i wouldn't shoot that thing unless my life depends on it, it bucks, it roars, it makes a lot of noise and fires a lot of bullets, anyone who knows warhammer 40K knows that those are the virtues that an Ork would look for in a gun. Also, it's impossible to fire a single round, you can only ever double-tap someone at the very least, try it. Just tap your fire and look on the ground, i garuntee you'll see at least 2 shells if not more.
Bottom-line is i'm a precision gamer, i like to fire fewer rounds for full effect; helps save ammo, helps me stay concealed if i've been sneaky, makes it easier to cap that dude who sticks his head out of his tank or the guy who looks round the corner.