The A6m's are actually very capable birds. The problem is that you need excellent SA to go with them. They simply can NOT take punishment. A6m's work very well for base defense or pure furballing fun. Just keep a clear eye open as to whats about to zoom in on you.
A6m paired with a faster bird becomes even more deadly.
Now when you surprise an enemy, he can't turn because the A6m will kill him, and he can't run because of the fast wingman. In short he's stuck between a rock & a hard place.
If your into long sorties, landing kills, killing bombers, A6m may not be for you.
But if your into instant fun via a big furball, don't sell them short. Also IMO nothing does the "hide in the CV ack while grabbing for alt" game quite as well as the A6m's.