Like with desktop computers, the choice of a web browser for mobile is a distinctly personal one. Different browsers can offer very different experiences.
The default browsers for Android and iOS respectively are Chrome and Safari.
Chrome provides the useful ability to sync with your Google Account across all the devices you use; you log in from anywhere and all of your searches, history and presets are saved to the account.
Helpfully, this includes auto-complete settings, meaning that if you have sites that you visit regularly where you have forgotten the specific URL, the mobile version of Chrome will supply those details.
Safari is the only possible default browser on iOS and integrates seamlessly with the other features of the phone. However, some other browsers offer features and design quality that it doesn’t.