I think MetaMask is safe on any of these browsers as there have been no known major attacks that have resulted in users losing their digital assets. However, phishing attacks can be used to access individual crypto wallet information if users are not careful. For maximum security, consider running MetaMask in a separate web browser and never keep your Metamask unlocked. Get into the habit of regularly clearing your browser cache, cookies, and history. Run anti-malware and anti-virus programs from time to time. I've been using Metamask in Chrome browser for a few years now as I have the EtherAddressLookup extension installed for added security.