The Yak has terrific views, is very fast, dives, climbs, rolls, either well or very well. The guns WILL actually hurt somebody and even take a couple bombers down. For the really good shots theres no reason they cant get 3 to 5 kills in one Yak run.
But best of all its fast, tough to nail down, and is a very good fighter at bringing the pilot home, at least I have found. The Yak is a really good plane to move up to from your 5 eny phase. I like it cause in some way it stacks up well against every 5 eny fighter. Either its faster, climbs better, turns better, dives as well, or plain out runs everything else. Just leave yourself a couple/4 thousand K of alt and/or dont slow down much past 250 mph.
The 9U is a great, great airplane.