Which way conserves more space when packing? Folding or rolling? & is this size luggage good for carry on?

I take each set of clothes....pants, top, jewery, whatever and fold it the width of the suit caseand lay it flat. You cannot believe how much you can pack. I pack 3-4 outfits this way. If I need more I can buy more at a usually very good price. No matter what you pack, it will probably not be what you want to wear there, unless you are elderly and don't care. KISS...keep it simplle, keep it stupid.