the Extreme is much heavier and more powerful so therefore a bit harder to fly. It comes in pretty fast when landing and will not glide as well as the Challenger.
I found that the Extreme can glide a lot better than the challenger since my brother had the challenger,and unfortunatly lost it,but before that we bought the extreme,its a lot faster so its harder to fly. I am a beginner and i have a go on it,its too fast for me.so i would go for the Challenger or the T-hawk as thats what im doing.