In terms of mechanical strength Yubikey 5 USB-A has the linchpin. When you plug the key horizontally into USB port and accidentally push it down with force while touching golden plate it bends and may break down. To prevent this I plug the key only vertically and touch it on both sides so as not to bend
In any case, the yubikey looks much stronger and more durable than the teresor. It would be nice to get the Trezor developers to think about improving their devices a bit so that they don't look like empty plastic boxes.
It would be great if the Trezor was also completely monolithic.
Agree, Yubkey 5 is strong enough if you don’t try to bend it. I think it’s also well protected from moisture and can work even after it’s been in the water (although I didn’t check it out). Yibikey 5 USB-C is even more stronger than USB-A because it has the metal shell around its USB connector. I don't have Trezor, I have Ledger and it also has the option to install U2F and use it for authentication but I prefer Yubikey to do this.