Installing a browser by default that cannot be uninstalled or even disabled then claiming it's the most installed browser, is a a little bit exaggerated. It's like Microsoft claiming that IE was the most installed browser on PCs, even if a great number of people only ever used it to download Firefox or Chrome.
Samsung Internet is great. It has built in support for content blockers, uses the Blink engine and everything renders well. I'd like to use Firefox on Android, but the performance and rendering on some sites is abysmal.