The only downside for metamask is add-on on Chrome and other browsers, no matter how careful you are you will make a mistake one day unless you don't use the PC to browse the internet, the more you have the metamask active and you are going from one website to another you are not safe, the mobile app is more safer
you can logout your metamask before you browse the internet to make sure that no one can screw you and dont visit sites that are not safe for work . i cant say if the mobile app of meta mask is more safer because phishing can happen outside and not the inside of the app but the app version is more easy and convenient to use .remember in crypto is never give your private keys even to your wife 
just follow these rules and your good.
Even if satoshi nakamoto is a well known person and he contact me through video call and I'm 100% sure it's him and he ask for my private key to my BTC wallet I will block him, it's as simple as that just follow these rules and your good. 