Haven't flown either plane too much recently. I do recall fighting a yak in an f6 and when we got slow it was over for the yak. I can also tell you the yak can loop with the best of them. At least from what I have seen.
Someone said somehing about the Yak turns better going right. That may be true. The yaks I killed turn fighting were both turning left.
The F6 can be tough to kill even wallowing. I've seen F6 pilots hit their flaps and it pops them in the air enough to dodge some rounds.