But one important point that is somehow overlooked is that for taste, brown spot don't matter, at all.
Depending on your guests, the preparation you're making, and your love of perfection, brown spots can maybe alter the looks of your dish. But they taste the same.
It would be a great error to prefer an unripe avocado over an over-ripe one for aesthetic reasons only. Unripe avocados are inedible. Over-ripe ones (within reason) taste perfect.