If you own a large amount of bitcoin, you should save it on a hard drive, which is safe for you, and of course you must own the private key.
I assume you're talking about an external drive? Storing your wallet files/private keys on hard drives or usb drives is just optional. Negative aspect is that they may corrupt, or just stop working completely. Best possible storage is a metal bar with the private key(s) engraved. This will make sure that your private keys will not vade or vanish as might be the case with paper wallets.
Conversely, if you regularly carry out transactions, and the number of bitcoins you own is average, you should use an online wallet that will support you a lot of things, and will ensure the time for Your transactions. Because online wallets always set a fixed fee enough to complete the transaction quickly.
If you choose a light weight wallet (light weight in the way that it doesn't require/download the entire blockchain) it will work perfectly as well. It doesn't cost much effort to just include a proper fee. What else do you need?
I agree with you. Now a lot of convenient applications. Each has its own characteristics and advantages. You just need to choose the purse in which you are most comfortable storing coins.