Well I just spent about 45 minutes testing the two. I found a flat spot of ground and crashed, leaving a nice fire and smoke as the "starting point" of my turns, then turned 4 or 5 complete circles at full speed, then again at ~70 percent thrust.
The Yak 3 certainly performed worse at top speed than it did slightly slower. The best I could get was approximately 10.5 seconds for a complete circle.
In the La7 I was able to squeeze out around 9.5-10. I'm going to assume you know the planes slightly better and that you could get the yak to turn a little faster--so I'll grant that they are even, or that the Yak is slightly better under these non-combat conditions.
The difficulty is that in combat, the La-7 would toast the Yak because its superior engine would allow it to Yo-Yo more effectively, (in the La-7, I was able to turn at much higher speeds).
Final analysis: more testing required, but so far I would take an La7 into a TnB fight over a Yak 3--but I DID learn that the Yak is better than I thought and that I'd be willing to fly it at least.
