For me, in terms of intensity:
IMAX 3 - toughest; least amount of recovery time between blasts;
IMAX 1 ("Interval MAX") - tough intervals but longer recovery time (blast 10 always gets me every time); and
IMAX 2 - the easiest for me (although my no means easy).
The choreography in 3 is the most complex, then IMAX 2 and IMAX 1 has the most basic choreography.
Blast 9 is the toughest in IMAX 2.
In IMAX 3 - blasts 1, 4 and 7 are the toughest. Blast 5 has the plie jacks.
Usually when she has a tougher blast, the step part is easier like in Blast 5, IMAX 3.
Marcy