One of the reasons that I insist on tumbling before resizing is that tumbling cleans the brass well enough to see it. That's important as eyes get older, but I have never seen brass split because of tumbling. Discoloration usually is not a reason to get rid of brass, but if it is pitted, badly scratched, deeply dented, etc., then if it is in a common caliber, why not get rid of it? Clean well, and you will be able to better see your brass.
