perhaps bluetooth?
Most important is plug and play on any computer without user action like installing drivers, if it can be done with bluetooth, why not, but USB has every computer and bluetooth only some computers.
The most important function is security though
Bluetooth would decrease the security, because anyone with bluetooth could try to crack the wallet, while with USB one would need physically contact.
Also I think it would increase the energy comsumption and the price.
i would never buy a hardware wallet it is not trusted there are allot of people who lost their coins trough a bitcoin hardware wallet and that is very bad. that have something to say about the security of the bitcoin.