It's too early to tell at this point. I really like the fact that Imax 3 challenges me, but I love Imax 2. When I first got Imax 2, I thought it was tougher than Imax 1. Now, I can do Imax 2's Blast Only Premix and ff through the recoveries. Right now, I see Imax 3 as being the toughest so I cannot wait until I see improvements in my cardio capacity and will be able to do the blast only premix of this one. As for fun factor, I really like the blasts of Imax 3, but I think I prefer the step sections of Imax 2. But like I said, it's too early to tell at this point. Imax 1 is still my favorite though - what a 'love/hate' I have with that one!