Airsoft Chay considers the Maruyama MP9 GBB as the best airsoft MP9, praising its realistic, high-quality polymer externals and well-designed steel internal components. Key positive features include its comfortable handling, modern controls, and an easy-to-access hop-up. The included QD mock suppressor effectively dampens the sound, and the light, 45-round magazines are noted for providing good gas efficiency in favorable temperatures.

According to him, this airsoft MP9 is not without its faults, including a non-full travel bolt (which can be fixed) and a non-realistic VFC Glock 18-style fire control group that shows signs of wear. The rifle is unreliable in cold conditions below 50°F and frequently experiences gas siphoning when fired on full-auto. The reviewer also notes that the trigger safety tends to break easily.

Despite these drawbacks, Airsoft Chay says that the Maruyama MP9 is an excellent value for its price, with superb aesthetics and feel, making its design faults forgivable. Whilst the cold weather and full-auto performance are disappointing, the reviewer ultimately recommends the MP9 and considers it superior to the competing KWA MP9.