In my opinion, the Coral Sea scenario was excellent. I rank it up there as one of the most-enjoyable scenarios I've played in, and I've played in almost 20 of them. I especially loved the aspect of carrier-to-carrier battles, with carriers that took a lot of hits to sink. Getting to fly torpedo bombers in it was very interesting -- I had never flown a torpedo bomber in a scenario before.
It is true that the US aircraft in that scenario were better in many ways than Japanese aircraft. This was mostly with the B5N2 Kate vs. the TBM-3 Avenger. The Avenger is clearly better. However, they both have to get low and slow to drop their torpedoes, and that does even it out some. For the other aircraft, the Zero and the F4F are decently matched, and so are the Val and the Dauntless. The F4F is sturdier and dives better, but the Zero turns better. Similarly, the Dauntless is sturdier and faster than the Val, but the Val turns much better and can be used as a good angles fighter even against F4F's because of that. The main effect of all of this was that we had higher mortality when we flew Kates than when we flew Avengers. Overall, having flown as both US and IJN, I think it was pretty well balanced.