I just bought my TZ24 today, complete with FEL, MMM, and Bush Hog. While I'm winding down from the stress of spending all that money, can someone explain to me what a box blade can do that the FEL couldn't, if anything?
A BoxBlade and a FEL serve totally different purposes. A FEL is sometimes used to dig, but is more suited to loading and carrying material that has already been piled. A BoxBlade (with or without rippers) is designed to scrape material, carry some in the box and then uniformly release the material. I don't believe they are equilavent in any way, even though a FEL could do some of what a box blade can do, but in a much slower and less precise way. A box blade is in no way a replacement for a loader.
If you have both a FEL and a box-blade then you have it made in the shade. Use the box-blade to loosen and redistribute large amounts of soil. Use your FEL to pick up and redistribute large loose piles of soil and again use the box blade to spread the spoils evenly and quickly. You can get a lot of work done using both in combination.
You NEED to buy the box blade if you really want to have some fun tractor time. They are worth their weight in gold. They also rip out small 1-2 inch roots like a twig snapping in your finger.