My mathematical friends and family tell me that LaTex is what is used further up the educational chain, at the postsecondary and professional level. So it would make sense that professors would find it to be the best.
EquatIO has the advantage that it has embedded voice-to-math functions.
If he is still struggling with keyboarding, you might look into using voice-to-math more, either inside EquatIO, or by pairing Dragon Naturally Speaking with LaTex or MathTalk (though MathTalk is pricey). I wouldn't be surprised if the existing dictation functions in Google for Education work with LaTex, too, though I don't know for sure.
Also, LaTex and EquatIO have some compatibility with each other. (EquatIO can read and write in LaTex.) So I don't think he actually has to choose between the two of them, in the sense that when he starts to notate in EquatIO, he can choose LaTex inside it.
