Sacrificing the ability to purchase their max amount of power points without requiring negative Qualities (and being unable to boost it afterwards, sans initiation) isn't a sacrifice; it's a bit unfair. Comparing it to Martial Arts isn't all that accurate, since you can buy Martial Arts after chargen.
A good example of the 'sacrifice' of being a Mystic Adept is losing the ability to astrally project like a normal magician, and being unable to receive power-points when you boost your magic, like a normal adept.
Maybe if you were allowed to purchase power-points afterwards with Karma, up to your natural magic cap (pre-initiation, to be clear) would even things out. As it is, anyone who wants to get the full bang for their buck as a mystic adept has to spend 30 karma on that alone at character creation, as well as pick the priorities that give them that full Magic stat. I don't know about y'all, but I do enjoy playing characters that are recently Awakened or Awaken in play; the current system really hampers improvement for a Mystic Adept (oh look, you're Awakened! Here's Magic 1 for some Karma, and... Well, you can't get power points after character creation. Sucks to be you, I guess).