Variants are discovered more often then not by comparing images.
I've actually found a fair number of variants in the DB over the years. One person owns a game and submits the information off their box. Another person owns the game and submits scans of their box. Then i happen by and notice scans have different info than what is listed on the page. Do some searching around and find that there are in fact 2 (sometimes more) versions of that game.
There are actually quite a few variants for modern systems that are not tracked right now. Mostly it seems like they are "rebrandings"/minor art changes. Some of them are changes to reflect accolades earned or a new publisher, etc
Keep your eyes peeled
