Most A6M3s performed very closely to A6M2s. Different engines, clipped wingtips, less gas tankage, and slightly increased ammo (100 rpg??) because it's belt fed rather than drum-fed.
However, pilots didn't like the loss of range, so those tanks were put back in, and they did not favor the loss in lift from clipping the wings. It also had the same type of engine the A6M5 had, but NOT the same performance. It didn't have the revised cowling nor the ejector stubs, nor the 20mph speed boost.
All in all, aside from clipped wing tips and a few more rounds, it's not much different than an A6m2.
I am, however, all for ANYTHING that gives the zeros more ammo!!! That alone is worth adding the M3