What are some alternatives?
When comparing Kingo 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
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.
One Click Root - Rooting lets you take full advantage of your phone or tablet.
Superuser - ChainsDD - Grant and manage Superuser rights for your phone.