It depends, I recommend you to use mobile wallets only if you really need it. If you can use PC everyday, then use pc version of the wallet.
MyEtherWallet is available in mobile, copay is also available for BTC, some of the altcoins have develooed their own android wallet. I don't think it's dangerous. You should use it carefully.
I think PC wallet is still the best for now for security and safety, it is safer than mobile wallet that people could easily have access to, but the only disadvantage is that one may not have access to PC wallet until we are close to the PC, but with a mobile wallet, one can easily be able to perform a transactions on the go.
Like many of others has also advised, I think the best would just be to probably hold both, either we leave small amount of coin for usage on the mobile wallet, that is utility tokens while we leave the investments coins and token on the PC wallet, its safer to loose utility tokens than to lose investment tokens.