I got a threaded model for my M&P. I've never really tried to gnat's ass my M&P so no clue if it helped with the accuracy. The factory threaded barrel had a significant POI shift with a can installed. The Storm POI wasn't noticeable. FWIW
I bought some for my "Non-Glock" Polymer 80 builds and one (non-ported) for shooting lead from my Glock 24C. They dropped in and shoot well, but not sure they're better than OEM.
I ran one of their conversion barrels for a long time in a G22. It worked great, but unless you need a threaded or ported barrel for some reason or reload there isn't much reason to replace the stock barrel with a stock length aftermarket. The only aftermarket barrels I've had issues with were older Lone Wolf barrels.