ORIGINAL: Divesplat
I don't think the rules call for anything different between the 2 disciplines(spins may be a different story) Pattern's 2007 AMA rules I haven't read yet but both require:
1) A break (some say the wing stalls but I hate that definition)
2) A rotation around the CG causing the tail and nose of the plane to make a cone shape
3) Stopping where the sequence requires.
I think that the main way that Pattern/IMAC depart on snaps has been in how you judge the displacement of the model. IMAC rules seem to be more realistic about what has to happen to the track of the model as a result of the forces involved to cause a snap.