IMHO I-Max is a tougher workout overall than I-Max 2. However, I-Max 2 has some absolutely killer training intervals (one-legged hops, straddle-taps on/off the bench that really build coordination as well as quad power, plie jacks combined with power hops, power uneven lunges on/off the bench with a turn, a 3-count over-the-top on a long bench with a squat at the bottom, plus the return of our beloved power-15's, plyo jacks, tuck jumps, side-to-side "slalom jumps" and airborne jacks) that you just can't live without.
Get 'em both. If you want to upkick the intensity of I-Max 2, just use the I-Max 1 warm-up, then start with the aerobic cycles of I-Max 2.
A-Jock