You should create a wallet that best serves your security desires and technological know-how.
Here's a great website that will help you sort through all the options and select one that is best for you:
https://bitcoin.org/en/choose-your-walletThere isn't one "best" wallet. There are different kinds of wallets that offer different features. Most of those features can be spread across a spectrum that has Convenience on one side and Security on the other. You want to find the right balance for you, the amount of your holdings for that wallet, and what you plan to use the funds in the wallet for (transactions or savings). For transactions you'll want convenience, for savings you'll want security.
But In general, you must NOT leave your coins online for a long period, you better have them in your own wallet. Electrum wallet is an excellent choice and pretty easy to use.
I've had coins held in an online wallet for years and have never run into an issue. But, that doesn't guarantee that an issue will never arise.