If I didn't list the plane type, you wouldn't be able to tell the difference between a Yak-3 and the Yak-9U in terms of AH.
About the only benefit of adding of Yak3 is if you put it in Normandie-Niemen colors so that there would then be a "French" fighter in the game.
Probably the next "Soviet" plane in AH would be the traditional Yak-9D, the midwar Yak varient. It compares to the Yak-9U, as the La5FN compares to the La7. Basically the Yak-9T we already have, with the single 20mm and x2 12.7mm MG's, instead of the big gun.
Of course I would hope that Pyro would finally give us the Yak-9UT that he promised us about a year and a half ago

But I'm not holding my breath.