What are some alternatives?
When comparing One Click Root and Sp Flash Tool, you can also consider the following products
Magisk - [2018.12.8] Magisk v18.0 - Root & Universal Systemless Interface [Android 5.0+] Magisk
Kingo Root - KingoRoot for Android is the best one click rooting software/apk with highest success rate. Boost your Android Phone by rooting it with KingoRoot!
KingRoot - KingRoot is an application that allows you to root your mobile device in a matter of seconds.
Root Genius - Root your Android phone with just one click.
unrEVOked - Unrevoked is a tool that provides a one-click method for rooting HTC phones that run Android.
Superuser - ChainsDD - Grant and manage Superuser rights for your phone.