One of the big differences is course size, OAA have course with up to 30 people on them, which seems a lot to me. FTE have a limit of 14 I think, CTC I'm not sure about.
There is alot a lot of uncertainty around OAA right now after the take over by CAE. CAE are changing things and changing them fast, some good, some not so good.
I sort of regret selecting OAA rather than FTE, although I must say the instruction is great.