If you have a properly made air-gapped wallet and a secure way to broadcast a transaction, there is no doubt that it is a more secure way than any hardware wallet, whether it is open source or has/does not have a secure element.

What you should always look out for is clipboard malware if you use a hardware wallet, which is why such devices exist, among other things. I'm not sure if it's possible to compromise a transaction that was made offline, and if there is a danger of clipboard malware or some other way for the transaction parameters to change the moment they come in contact with the infected online device?