I am using MyEtherWallet because it is compatible with ERC20 tokens. It is safe as long as you do not click anything that may be a phishing site wherein you will input your private keys. Usually, you will receive e-mails from those phishers telling you to update something so don't just immediately click anything you received because there is a risk that they will be able to have access to your wallet. Always check the URL when accessing the site because the interface would be the same so you will not notice immediately if it is a phishing site or not. Always triple check the address. If you want to be more secure then store in a Ledger Nano S which is a hardware wallet. It would be safe because it is stored offline.