To begin start to use the right terms, and if you want Trezor, Ledger or any other wallet of that type, in that case you want hardware wallet. For now, this way of storing coins (private keys) proved to be one of the best or the safest way for cold storage or for daily use.

As a user of Ledger Nano S I can say this device does what its primary purpose is, it is keep private keys inside of device and this is most important. Maybe I'm not happy with some other stuff when it comes to Ledger, but safety is the most important factor for me.

In the choice between Ledger or Trezor the main factors when choosing are design and price, everything else is less much the same. It is also important that the device is ordered from the official site of the manufacturer, and to avoid buying used devices.