MyEtherWallet is being rebuilt as MyCrypto, which will potentially scale much better.
For daily transactions, MEW/MyCrypto is a good choice. You can send and receive ETH, generate transaction offline, and interact with Ethereum smart contracts. However, if you want to use Decentralized Applications (DApps) e.g. CryptoKitties in your web browsers, you should use MetaMask or similar browser-extension-based wallets to approve your transactions.
Both can be used to invest in ICO.

Another note is that using Metamask is safer for most beginners because it manages your keys for you.