I have flown both, though different sizes. 10 years or so ago I had a Goldberg Sukhoi and I absolutley loved it. More recently I got to fly Wayne Voyle's 37% Sukhoi and it was awesome. I didn't ask about his pitch mixes but the airplane didn't seem to have any bad tendencies. Of course it is hard to judge from just a few minutes on the sticks. I have several hundred flights on my prototype Yak-54 so I feel more qualified to speak on its characteristics. I'll try to do so without making any commercial plugs and getting in trouble with the moderators. When designing the 87" Yak-54 it was very easy to get the wing, stab and thrustline in line while staying within the 10% deviation parameters. I have no mixes whatsoever on this airplane. It is the closest I've seen to a "pure" aerobatic design. It also rolls incredibly axially and has incredible knife edge capabilities. I feel these are its advantages over the Sukhoi.