I am putting together my 12" 6.5 build from the faxon group buy. This is my first 12", I have a 10.3" 5.56. I think I want to go with an adj gas block since this weapon will only be shot suppressed, and I know the 12" will send more gas back than my 10.3. I have never used an adjustable block before so had a couple questions...

I have seen a lot of folks using the SLR and I have seen the superlative arms "bleed off" setups, any advantage of one over the other? Is the superlative reliable or will it allow build up inside the block?

No they both advice the same effect but one leaves the gas at the block and the other pushes it out the barrel. I prefer pushing it out the barrel.

I'm using a Odin works AGB,  it seems to do the trick, seems well built, and it has plenty of adjustment.

I have SLR on a 16" .308 and an 18" .223.  I don't have anything on my two 10.5" SBRs and they run fine suppressed or not.  I did have some cycling issues while I was working up loads, but once I got them within proper pressure range they both run great.  

Adco shortened both of my barrels and if they adjusted the gas port, they sure did it right.

The SLR won't build up and jam the screw like a lot of them will.  Instructions simply say to close it when cleaning the bore.  The SLR has 14 click positions, so it is easy to know what numbers to use.  I wouldn't consider any other type unless it was a similar design.  I studied them for a while before jumping on them.  The 16" .223 runs fine wide open without a can.  Once it is broken in I will try the can and shut down the gas a bit.