I have 3 - a plain one, which I keep for emergencies (like the time the one I usually wear fell out of my bag), one with rank stripes (which is the one I usually wear, as when I wore the plain one my students asked why I didn't wear the one with the shiny new stripes my instructor had just given me), and one with my name and rank embroidered on it that I keep for seminars, testings, and other events where it is useful to have my name clearly visible for people who are looking for me but might not know me. I usually only wear it with my "dress" uniform, which is the one I don't work out in and get all nasty with sweat stains.