From Guns.com:

The new 9mm M&P Shield Plus, which comes in both standard and Performance Center models, comes with 10- and 13-round mags while keeping the same traditional frame – and therefore holster – size as the legacy Shields. Other new additions are an updated and optimized grip texture and redesigned trigger. S&W says the flat-face trigger will give users a consistent trigger finger placement allowing for more accurate and repeatable shooting, while the new stippling on the grip texture allows the user to manage recoil, keep a firm grip, and not irritate the skin while carrying concealed.