I am more of a box-blaade fan than a rear blade fan, but that's because I could never make the rear blade work right.
The box blade allows you to, by adjusting the length of the top link, vary the amount of bite you are taking into the ground more than a rear blade. The side panals allow you to move more material around and will automatically fill low spots once the box is filled. Scarfer teeth will break up hard packed material and allow the box to carry it.
The rear blade can be angled which allows wind-rowing material which is more difficult (impossible?) with a box blade.
More experienced people may be able to add more for the rear blade.