In theory, either should be just as secure as the other as both are designed to never expose your private keys online.

Things get a little more complicated in practice. Just as other users have said, it's far too easy to mess up the creation of an offline wallet if you're not tech-savvy or careful enough. On the other side of the fence, if you go for a hardware wallet, you're essentially trusting a third party to create a secure product for you; the same isn't true for offline wallets because you can go for open source projects you can personally verify every step of the way. Another factor you would have to consider is that hardware wallets are a target for malicious entities because they basically announce that they're keeping a significant amount of money.

I'd personally say air-gapped wallets set up correctly are safer than hardware wallets, but I don't think any person has lost any coins over either so far, so you should be safe no matter which way you go.