It's vision, Akers has it, Henderson not so much, however, you're correct, Henderson is more explosive and IMO, McVay just needs to give Hendy more carries to get into a rhythm, plus Henderson catches the ball well, however, McVay does not trust Henderson with pass protection and that's why you will see Brown in their more often on passing downs.
The other issue with Henderson, is the more you use him, the more prone he is to getting dinged up. He's like that nice sports car you store away for the winter, but when you bring it out in the summer, you still can't put many miles on it.