Thanks David.. Ive heard some similar things....and Im currently using a 57 on the outside and there is some blaze to it. Most in the audience here have little regular exposure to the button box. So I guess I get an easy out there in most cases.
Since I fairly sure my eventual playing will be with an electric band, Im starting to figure an internal mic is best if not to just be able to isolate the sound....
The choice between internal and external mics depends on the type of sound you want. Even with the exact same mic, the results are VERY different. If you want to go for a Cajun sound, it is best to have the mic on the outside. This gives a nice clean sound. But for zydeco, it is better to put the mic on the inside. This creates that cool muffled sound that we associate with zydeco greats like Keith Frank(the sound is somewhat like what a blues harp player gets).
On my D accordion, I have the option of switching between internal and external with the flip of a switch. I suppose I could even use both at the same time, but I haven't tried that. Lately, I find that I just leave the external mic at home.