If you're going to run a suppressor, go with the 11.5" upper. Either get it as a factory SBR or set it up as a pistol. If they should ban the brace, you can simply remove the brace and be legal. If you get it as a pistol, you can Form 1 the AR and run a stock when your stamp comes in.
However, don't fall victim to "Analysis Paralysis". Both are excellent choices. Pick the configuration you like best and get to shooting.