the yak gun package isn't that bad...last night I landed 5 lancaster kills for example. Someone compared the gun package with an early zero but thats not exact, the Yak9u got 2x its firing time with a better 20mm, and has dual 50cals which isn't something to underestimate.
Good speed, and if you know how to play with the throttle a late spit won't shake you. Also the yak wings never come off, its important if you get into an heavy furball. A problem is that the pilot is exposed and a pilot wound/kill is quite frequent.
As gixer said its well adapted to MA because you always have the edge on something against nmy cons, like speed against spits, tun rate at low speed against pony, verticals against F4U...109's and La's are troublesome thougt.
Another great 20 eny plane is the spit9.