Visited LGS today. MPX k was $1850.
Controls and handling are standard AR and ambi. Trigger is surprisingly good, tickling excellent. Would buy in a heartbeat. Downsides to me are the proprietary mags and stupid Sig muzzle thread pitch.
Ended up comparing head to head with a B&T APC9 G $2500. Controls similar to AR, trigger is OK, to meh. Little take up and a decently clean break. Safety is a bit stiff and the lever is clunky. It is a 45* throw. Personally I like the forward, folding, non reciprocating charging handle. Not just cool factor, you can clear malfunctions and charge the gun without changing your shooting grip, head or body position. Also plenty of cool factor. 😄 The charging handle also moves a deceptively short distance. Like less than 2". Weird,( but good) when your used to a big 5" AR tug
Ended up with the B&T.
GLOCK MAGS were the main reason. I have a AR9, Glocks, and a stack of ETS 33 rounders. (MPX mags are $65+ each) B&T lower is swappable for other mag styles and the upper is the serialized part. Useless for me, but cool.
Comes with sights and 3 lug suppressor mount. (Not included with MPX and odd muzzle thread)
Reviews- most of what I've read says the B&T's proprietary recoil system is the smoothest shooting SMG/Pistol out there. The gun was engineered to be controllable firing FA.
Brace- the SB brace is just way more substantial than the tail hook style on the MPX. Purely personal preference, the tailhook style looks much cooler and it's lighter.
The only two downsides are fixable. Meh trigger and the clunky safety.
In a pinch I'd pick either one in a heartbeat. The MPX k ended up sold as well. To a elderly couple with a business downtown. Think they were surprised by the WA 10 day wait...