I have both Crossfire and To The Max, but find myself doing To The Max at least a couple of times per month whereas I have only even tried Crossfire twice (although I was just telling my 9-year-old I should give it another try because everyone loves it).
I too worry about high impact, but find that To The Max is somewhat gentle because much of the time you are jumping up onto the step, which lowers the impact (for an explosive movement). Plus I think between the thorough warm up and opening solid step segment, you are really ready when the jumping begins. And the breaks are very helpful too.
I hurt my foot doing Crossfire doing those turning jump things where you put the stretch band on the floor. I just landed funny I guess. I am going to try it again with a different pair of shoes and see if it is better..
The music in To The Max is so perfect for the moves and motivating beyond belief, and that is also why my son finds it his favorite as well.