Hardware wallet is secure and easy too use, but has some vulnerability and database hack. Even though they vulnerability has been fixed, it's doesn't prevent from other undiscovered vulnerability.

Air gapped storage can be the most secure wallet (but it's not 100% safe since malware can still infect) if you know how to set up properly, using right tools and know various malicious attack that can steal your Bitcoin even using air gapped storage (e.g. malware).