The difference is the time until the starter matures. Without going into the maths behind, just remember that growth is exponential, not linear.
My favorite source (in German, sorry), uses 10-20 % of the flour weight. That means that the starter will need feeding about once a day, as opposed to the equal weights approach, where you feed twice a day (or even thrice, if you have an exceptionally active starter). I wouldn’t go below the 10%, just to make sure nothing unwanted can get a chance.
So “correct” is what fits your feeding and baking schedule, as long as the starter ratio is somewhere between 10 and 100% of the flour weight and you give it the correct time to mature.
Remember - the principles of sourdough have been used by humans since way before the invention of scales. So while weighing is something we often recommend (at least as in “use a scale, not a measuring cup”) for bakers who aim to get reliable and reproducible results, learning about the characteristics of your specific sourdough, its demands and behavior, and how to tweak it to match your needs, is in the end way more important than the ratio of starter to flour.