The Ledger Nano S supports more coins and is cheaper.
Both have good reviews on Amazon.com. I recommend to only order from the official website. Never buy a used one. There are a few one-star reviews giving serious complaints of receiving a fake ledger, so even amazon is not a safe place to buy your Ledger or Trezor from.
I would personally buy a Ledger Nano S: it is widely used and the price is good.
I don't like that it uses Chrome apps. This feels as unsafe as Ethereum's Parity running within a browser. Google is also discontinuing their apps - only ChromeOS will be able to run Chrome apps. Therefore Ledger is currently developing their own product. I hope it will be available in time and fully bug free. Projects on a rush often have problems, so I have my reservations.
If you want more security and only store Bitcoin and Ether, you can look into Trezor as a safer alternative.
Here's a more complete writeup:
https://www.buybitcoinworldwide.com/wallets/#hardware-wallets
If you own more than $1000 in Bitcoin, Ethereum and other currencies combined, I would recommend to use a hardware wallet.
Many people are keeping their coins on exchanges. MtGox, Bitfinex, Poloniex, Bitstamp and Cryptsy have all been hacked, so they are not fully safe.
You've heard it before, but you STILL are doing it. Moral of the story, do NOT keep coins on exchanges unless you are day trading.
A hardware wallet is in your house (offline) and a hacker needs your 4 digit PIN code to operate it. That's why its the most safe option.
