Talk to the math department at your local college. All the professors there use LaTeX or Microsoft Word. Look at the papers in LaTeX and the ones in Word. The choice is obvious... LaTeX is free and everything looks like it came out of a technical journal, Microsoft Word is expensive and makes everything look terrible. By the way, when I say that everything LaTeX makes looks like it came out of a technical journal, I mean it. It's hard to write LaTeX that doesn't look like it came out of a math journal. LaTeX is not as easy to use, but it is very mature and there are books on it.
MS Word is good enough for high school, I'll give
>>4 credit for that. But it is not really good enough for college math, and it is downright embarrassing in grad school (well, in some disciplines... they still use underlining in English departments, as if someone forgot to tell them that they don't use typewriters any more).