You wouldn't use a PC-based wallet -- what does that mean? The reference client is a PC-based wallet. Are you saying you'd only use a hardware wallet, or a paper wallet (generated on offline PC)?

The most important distinction to make is where your private keys are held -- online or offline. I figure any online desktop wallet is a target for theft, but I don't particularly like hardware wallets either. They have fairly large and untested attack surfaces, multiple theoretical attack vectors, centralized firmware updates, etc. Major vulnerabilities have been found (and quickly patched) as well, just like Electrum.

Electrum can be used such that private keys are kept offline on an airgapped device. That's why I use it. It's also got great UI, is lightweight, Segwit-compatible and can be used in conjunction with your own full node. Lots of selling points!