MarkH,
To imphasis a bit more on what other's have said, its very easy to SMOOTH/GRADE ground with a box blade. I can't do that with a FEL. I have a top link on to run the box blade and I would hate to have to use the implement without the top link.
I'm clearing some ground for pasture right now, I spent all day yesterday cutting up timber slash and downing small trees, the box blade and the 4n1 FEL or great companion tools for what I'm doing. I can move stuff forwards and backwards which makes things a bit more productive. I can use the box blade USUALLY without digging into the ground if all I want is to move wood. Its taken quite a few hours to get the FEL just right to move wood and not dirt and wood.
The box blade and the FEL are complementary tools as far as I'm concerned....
Hope this helps...
Dan McCarty