From everything I've read on the subject, the ledger nano s is the best option for the money. Both are good, but the nano s is a lot cheaper. Trezor support more ERC-20 tokens as far as I know, since it supports all, and ledger only supports a few, but if that is not a problem for you go for ledger. I also heard that the software of the trezor is better. Not saying that is more secure, just that it gives you more options, but nothing really important, so it all comes down to what is the wallet that supports all the coins you want to use. If both do that, then the less expensive is probably better.