we sell both, I have owned both
the 5 spot is a great bike
basically, the differences are:
the 5 spot is plusher/more travel with slacker angles and a longer wheelbase which gives it more stability
the 100X is not as plush and is quicker accelerating/climbing and cornering
sizing also runs differently, so, definitely take that into consideration
basically you need to assess your needs/wants/priorities, where you live, i.e., tight stuff or more open stuff, etc....