I would suggest getting the high school diploma. It's really a matter of perference really.
-Although you could graduate early, and I'm sure most of us could, but going to school is half the experience (good or bad). It may help us develope different skills for later.
Though, to say universities don't accept them... well that's not really true. If you're going straight from HS to a major university then perhaps many would look at a GED as "less."
But if you got a GED then goto community college, then it doesn't really matter. Because once you're in community college, take the entry test (which is the TASP test in Texas) then you're in. There isn't really a pass or fail, it just decides whether or not intermedial reading, writing, math or whatever is needed. If not, your in good to go. Take a semester or two then transfer the credits to a Major University. After a year or so in college (University or Community), hardly anyone looks at your SAT's, ACT's or whether or not you have a GED. They base your acceptence on transcript and course load.
Well because SAT's and ACT's help you get accepted to a university. And if you already been accepted to a college (including community) it kind of nullifies that stuff. Though I'm sure there are exceptions like some private universities.
Seeing you're only 15yr now, I would give it a year or two. If not, you may really miss some stuff, not necessarily educational wise, but just being a kid. That's just me. I mean, public school aren't "that" bad, I attended one all my life
Just follow what you feel is right.