Linux Mint is not insecure it provides a great updater system that you can have even more control over.
Ubuntu doesn't give you control over what types of updates are installed...you either get them or you don't.
I am a HUGE fan of the Linux Mint Updater because it provides me with the ability to give family and friends a Linux based system that I can safely show them how to do updates because the stuff that could break the system can be turned off and wont be presented them to install.
Then I can activate those updates when I am there to fix it if it breaks something rather than them updating and then freaking out because something broke. I don't have to worry about that happening.
With Ubuntu my Mom has over 100 updates to do because she is too afraid to run them as they could break her system but more importantly when she first tried to run them the system failed and gave her an error message that she didnt understand of course. So the updates just kept piling on and now the system simply can't update due to the amount and the conflictions they introduce.
Ubuntu's update method has its own flaws.