Just like the supply of BTC, there are only 21 million BCH that will ever exist. There are even less in circulation, which makes BCH just as scarce as Bitcoin. However, supply scarcity only matters when there is a demand for the asset, and there is not much demand for BCH currently. Bitcoin Cash was listed as one of the tokens that PayPal will support, so that could change in the future with more adoption. But even then, Bitcoin is a better investment.