I've taken as long as 7 hours descending the main trail -- had major toe pain. But 5 hours is pretty good time.
Going down the MR is quicker, if your quads can handle the steep descent. The main trail just seems to go on forever with those switchbacks and gentle descent.
You will meet far more people descending the main trail, if that is what you want. The MR is much more a quiet wilderness experience.
