The air superiority fighter (ASF) for the soviet union is, if not the best, very close to being the best in a lot of ways. Like all ASF's, you need to wait out a bit more compared to an interceptor call-in, but boy is it worth the wait!
The soviet La-5FN has outstanding turnspeeds, allowing it to aim down enemy aircraft without any problem at all. Most aircraft are destroyed in a couple of shots from the La, meaning that a craft goes from healthy to dead in less than a second. ASF's are pretty ineffective against ground forces, as their weapon has a shotgun-like spread, but the fear value still applies nicely. The increaced damage is also noticable on larger ground targets like Vehicles and even deployed HMG's can take some damage if you're lucky. But really, if you're using high-end dogfight kings of the sky against those pesky, muddy, uncivilised land troops then you're doing it wrong... way wrong.
In most cases, you will prefer the La over the Yak as it's just better at being a fighter, while the Yak is more universal in application.