Jwteknix said he likes the looks of his heavy profile barrel better. I'm just saying I don't want to have to carry a heavier barrel around.
I don't know how the barrel of your rifle is profiled under the handguards, but from your description, it sounds like you made a good choice. As you say, that hideous S&W flash hider weighs 4 ozs. I know, because I weighed mine after I took it off and replaced it with a BABC. The barrel of my M&P-10 is pretty skinny forward of the GB but it's profiled heavier under the handguards where the extra material is needed to deal with the heat. It's profiled much like a sporter weight barrel of a standard bolt action rifle.
It's kind of hard to see in this photo because of the shadow, but this shows the profile of the barrel
I say it's the most sensible choice of barrel profiles S&W could have made for this rifle. Is yours similar?
My Big Smith with NF 2.5-10x32 NF scope, Magpul MOE hanguard, Moe grip, CTR stock, a loaded 20 rnd Pmag (1.5 lbs) and sling (.5 lbs) weighs a total of 12 lbs, 11 ozs checked on a scale. I may have shaved 2 ozs off that when I swapped the S&W flash hider for a BABC