Hi Russ!
I play along with midifiles quite a bit, since guitar is my main instrument. As long as you use your instrument along with the files, the way I see it, you're just one in a virtual band. You are in fact doing exactly the same as if you had a live band, with the exception of interaction.
The arranger part I use for marches, polkas and sing-alongs in weddings etc. Plus I can build excellent midifiles with the styles. To say that using styles is 'better' than playing with files is a matter of interpretation. There are different views in this crowd of members. I think even the 'style-players' use midifiles at times.
Best of luck!

------------------
Roy-Andrè