ORIGINAL: MinnFlyer
There's really not much difference between the Citabria and the Decathlon. In the Full Scale versions, the biggest difference is in the engine used. As far as the Sig vs. Midwest, the sig is a much smaller plane (.35 size) while the Midwest is a 60 2 stroke or 90 4 stroke.
There is another significant difference though Mike, the Citabria had a flat bottom wing while the SD had a semi-symmetrical wing for better aerobatics.