I like that securus is constantly improving their service, they are always adding new features to make your experience better! They also have great customer support when you do need help with something (but don't expect it).
The only thing about them which could be improved would maybe just being able to see who has been in contact before or after me for any reason - but this isn’t really an issue as much anymore since we started using another provider instead of phone verification/identity checkers etc..