Prefix: I am *not* a great pilot!!
But - the Yak-9U is my love
It climbs, it dives, it zooms, it manages E quite well. And it's a speed demon. It's best in the mid- to low-level fight (say 15K or under), but that's where most fights happen anyway. I don't consider the ammo load a limitation - it forces you to angle your way to the optimum shot. If I see someone spraying and praying, I just lick my chops. Dinner
I can say that there is no plane in the set that the Yak deosn't have at least an equal chance against. In many cases, the Yak simply dominates. The Yak usually has one or more advantage against at least 90% of the planes (maybe more).
The LA *might* be the exception: they seem to outclass the Yak on paper. But very few *good* pilots fly the LA, except for base defense. So if I see one far from home, I'll merge and see what they do. If they do something "stupid" (by my standards, which are *not* uber), then the fight's already over.
When I'm in a Yak, planes that are very good in the vertical worry me more than others. But Ponies, Corsairs, and other "slow-climbers", starting co-E, it's just a matter of time before their E is bled dry and they flop. This should *not* be taken as a slam against the wonder-sticks in those plane types, of course!
The only type of plane I *don't* engage is bombers. But that's just because of the ammo limitation: It simply takes too much to shoot one down.
Spit 16's are the yak's biggest threat, as it does everything the Yak does
Except that the Yak is far faster. My engagements against Spixteens usually involve merge and a few turns. If I don't have angles, I'll simply extend out to 2K, rinse and repeat. You can't be "forced" into a turn fight. You either let it happen or you don't.
To be perfectly honest, the only plane I fear when I'm in a Yak is another Yak