It is my opinion that box culverts (single and multiple) are used where;
1) greater capacities are req'd. (fill ht. and or volume of h20) ....boxes come in larger sizes
2) there is the ($savings) practicality of casting in-place, vs. precast pipe or precast box.
Reinforced Concrete Pipe or RCP (cir. conc. pipe) standard sizes are:18,24,30,36,48, and 54", There are larger sizes...from about 42" on up it becomes significantly harder to place, connect and backfill CORRECTLY especially when placing double or triple sections in the same location.
My answer to your question would be money....if the hyd. needs can be met with both items.
One more point. I have noticed that the suppliers of "wrinkled tin" culverts have gone to asphalt coating for protection. Ordinary galvanized metal culverts don't like the situation where salt is used on roads for ice removal, requiring early replacement down the road. Of course if you are willing to let someone else worry about that later, replacement is not your concern now.
Then comes plastic pipes. They seem to be used a lot, but I have no idea about longevity.
Think about problems that may come from erosion at the ends and possible failure by taking out the earth support, which can happen with concrete pipes. Flexibility has some benefit where erosion may take place.
Load carrying ability is something the salesmen will give you all sorts of scoop on. It is amazing what earth arching can do.
Box culverts also come in handy when you have height limitations. You can get them in varying size rectangles as opposed to the normal square sections. Eliptical and arch pipe do the same thing, but I don't believe they come in the larger sizes like box culverts.
