I think most users first look at price and design, and you should visit their official sites and see what device would suit you more. In terms of price Ledger Nano S is a little cheaper (around 60 EUR), and Trezor One is 69 EUR. For users who can wait few months there will probably be additional discounts on Black Friday or in time of Christmas and New Year holidays.
Both devices are enabling safe storage of user private keys, and this is most important when it comes to hardware wallets. I am using Nano S for some time, and generally I can say that I am satisfied. There were some minor problems in past, but nothing serious that would endanger security of my crypto.
I also intend to buy Nano X by the end of this year, and use it on the go paired with my smartphone when I need to pay something in the physical store.
For this reason, it is most important to have a safe backup (24 words seed), and if device is broken, stolen, or damaged in any way you can always restore your wallet to any other hardware device, or in most desktop wallets. I am not sure how long one hardware wallet can last, it depends how it is used and stored. My Nano S is in mint condition after one and a half years of use.