A box is good for pushing snow, a straight is good for rolling snow. All depends on the set-up of your lot & what your are installing it on.
I'd go with a V plow, or even a Blizzard 810 (the new talk of the board), that way you can have the best of both worlds.
With a Box your plow wont trip as easy, unless you get something like the turky wings.
I have a 3/4 ton with 7.5' blade for that site. There are some big open spaces to the parking lot and 3 or 4 long laneways about 50' wide by at least 500' long with a requirement that does not allow me to leave a ridge of snow along the sides of the lanes.
I haven't heard the term turkey wings before. I was thinking of making my blade into a box with some 12-16" side walls with brackets all attached with pins for easy removal.