There are tons of wallets out there to support the expanding altcoin ecosystem, and some are arguably more secure than others. Also, some wallets support only one cryptocurrency, while others support multiple cryptocurrencies. It is best to first understand the various wallet types: hot wallets, software wallets, hardware wallets and cold storage.
Hot wallet refers to a cryptocurrency wallet that is online and is connected in some way to the internet. Bitcoin/altcoin hot wallets are used to pay out withdrawals instantly, like if you wanted to buy something on the fly. Coinbase and Blockchain.info are examples of hot wallets. Also, wallet apps for both Android and iOS are considered hot wallets.
It is NOT advisable to store large amounts of cryptocurrency in hot wallets, particularly hot wallets issued to you by cryptocurrency exchanges. This is because the exchange is in control of your private keys and if they get hacked, your coins could be stolen. Some exchanges, like Mt.Gox and Bitfinex, have been hacked in the recent past, and it is estimated a that more than $1 billion worth of investors’ cryptocurrencies have been stolen as a result of these hacks.
Software wallets are a type of hot wallet, but on your personal desktop/laptop or mobile device rather that being stored on an exchange. Usually the creators of an altcoin will create a wallet app which you can download to your computer or phone. In short, you have control of your wallet via your computer or mobile device… but, if you get hacked or your device is damaged, you may lose your coins forever. These fears of hacking and damaged devices are the reasons that hardware wallets and cold storage are becoming more popular.
Hardware wallets are surging right now due to web wallets and/or exchanges being hacked. It is always better to keep cryptocurrencies off of exchanges unless you are actively buying/selling them.
Ledger Nano S
The Ledger Nano S is a great hardware wallet, with support for many altcoins. Plus, Ledger is actively adding more apps to the Ledger ecosystem in order to support even more altcoins. As of January 2018, Ledger had already sold more than 1 million Nano S wallets!
Trezor Bitcoin Wallet
Trezor Bitcoin Wallet is also widely used and is fully open source. It supports bitcoin and several altcoins natively but you will need to use MyEtherWallet as an interface for ERC20 tokens such as Ethereum. Despite this, Trezor is a very secure device with a solid reputation.