There is one tangible difference between a box and a programmer. The programmers, in addition to adjusting fuel and timing curves, also have code readers built in and can adjust your speedo for tire size. SMARTY, SuperChips and HyperTech make handheld programmers for the VP trucks. Maybe others, those are the three I know of.
Some of the boxes, like the Juice, Quad and others, require that you "tap the pump wire" which *some* people find objectionable. It can void your pump warranty if you have any remaining, and it has been known on older VP's (98 and 99) to seize the rotor.
You also need to begin with the end in mind. If you intend to cross the 500HP barrier, you are most likely going to have to stack a programmer and a fueling box. If that is your intention, you might want to start with a SMARTY. If you only want a little kick in the shorts for towing (40-60HP) then a Puck or EZ are probably the best choices.