RE: Pitts Model 12
The Ultimate will be the better flyer.
The Pitts has a very short tail moment, which makes it snap like a demon, but it can easily get you into trouble.... as I found out the hard way.
The Ultimate will fly in a much better than scale like manner with the 4C 56 you are contemplating to use, but neither plane will have unlimited verticals with that engine, but it will do verticals though.
The Saito .56 4C is akin to putting in a .32 2C glow engine... which the Ultimate does handle very well.
There is a review here where someone installed a 2C .32 and a 2C .40 LA engine.
In spite of the fact that the .40 LA was MUCH weaker than the engine you are planning to use, he liked the plane's performance with it.