Whatever works you you, folks...I DON'T use MIDI files of any kind. I try to avoid using an arranger like the plague, and most enjoy group work...the interaction between musicians which only works live with certain kinds of music (read-jazz) and with players of equal ability.
There is a market for this approach for me and probably for any accomplished player who wants to specialize in this kind of work. About 40% of my jobs are keyboard and drums...20% as a single and 20% group work.
I say, choose your weapon (arrangers or whatever), learn how to play/operate in real time and JUST DO IT!
Good luck!
Russ