The blade on my tractor hooks up to the 3-point hitch on the back.
It has the following adjustments:
1) Swing the whole implement right or left on a vertical post located just behind the hitch. This lets me set whether I want the blade to be cutting directly behind the tractor, or off to the side.
2) Rotate the blade right or left on a vertical post above the blade. This lets me set whether I want to throw dirt off to the side, or drag it with me.
3) Rotate the blade clockwise or counter clockwise as viewed from the drivers seat. I use about a 30 degree angle to dig ditches. On my tractors the adjustment on the lift bar is only good for a few inches of variation. The adjustment on the blade is good for a few feet.
The box cutter pretty much only drags or pushes dirt straight forward or back. Those rippers on it though do a better job of breaking up hard soil, and i find it easier to grade with a box. I remove the rippers for doing finish work. The lack of adjustability is it's primary failing for cutting swales.
Another strategy that I have used for ditch-digging is to till the area where the ditch is wanted, and then run the scraper over it to move the dirt. Repeat as needed.