Some well thought out comments here, here is mine though it wont count since I am not an artist. I don't care for the proof factor that since an image shows it's borders it is more "pure" than one that is cropped. A print in my opinion looks very amateurish with the border left intact in the print.
The photographers of the past who were my teachers went to great lengths to mask the borders on their 8x contact prints. Any print printed that still
had the hold down borders and code notches etc were considered to be a "proof" by most buyers and D R technicians. In the mid fifties or so the "purity" of an image began to be challenged by a small group of "artists" that if it did not show the borders you had done something unsanitary or unclean by cropping the negatives gender. (border to me) There fore any thing with out the negatives edges was automacally a second or third class image. The only good or great image had to show it in it's entirety. That small group I mentioned is now a much larger group including many of the large Format camera operators.
I will not leave the border on my prints, but I really don't care much what others do. I still look at a print with edges showing as a "proof" or unfinished.