IMHO, no. Although you can grade with a rear blade, you can't really break up subsurface with a rearblade, nor can you with an FEL, unless it has a toothbar (and even then it really isn't efficient for that purpose). The scarifiers on a boxblade allow you to break through small and medium sized roots and loosen rocks while collecting material in the boxblade.
I find that a boxblade is MUCH more versitile and useful than a rearblade and is a better combination with an FEL for earthmoving work. Of course, for just light grading, pushing material off to the side of a driveway, a rearblade should be fine.
Hope this helps.