i very rarely use the sd, its fun and all but i prefer the regular ole M4A1 loud as hell"bangin and sangin" the sounds of death so ppl know im comin. the element of surprise is more than silently killin folks. you can overwelm and surprise just as quick comin in loud as hell.by this you have the added shcok value of "my god this dude just rolled through the middle and killed 2 guys and hes comin for us" and make ppl get nervous and backpedal to try and recover areas.
also by rollin in loud you have the advantage of ppl cmin to you to get kills instead of always runnin and lookin.trust me when they come to you to be killed its alot easier

but think id go as high as 80% if not more run to noise.i mean i do sometimes depending on situation but you go to help or get the guy that took your teammate out and bab you just got layed out too.in order for this to work though you have to have your game on point, no stressin, no hittin reload during battles only before and after a firefight if needed.and you have to be able to control your loud *** wep of destruction and watch all sides for more free kills :P:D