there is a BIG difference between the two.
Knewton is adaptive and learns from you. this means you study smarter. the system targets what you dont know and what you need practise on not spend time on what your already good at. and as you keep practising and doing tests etc it keeps adjusting and modifying the content to suit your current level. it targets specific atomic concepts.
Gmax doesnt. gmax gives you access to online cats, homework, videos etc but the whole online course is not adaptive and built around you. rather its an assimilation of offerings from different producers bundled into 1 with videos as well.
Dont get me wrong gmax has some awesome videos. But knewton is much faster and smarter. and you still have access to a ton of videos, live classes, email help, weekly live office sessions, tons of practice material eg tests homework etc.