Edit: Oh yes forgot to add that both Mycelium and Electrum support bech32 addresses so are Segwit enabled. So that's a great add on.
To make this not confusing, bech32 addresses are the segwit addresses and all bitcoin bech32 addresses start with bc1. The P2SH addresses are not truly segwit but a compatible address which can receive bitcoin from segwit, legacy and its own addresses.
The safest bitcoin wallets are hardware wallets like ledger nano s, airgapped devices and paper wallet but for convenience, hardware wallet is better. The best online is still the bitcoin core but many could not have access to having enough data to download the whole blockchain and go for electrum on both computers and mobile phones, and mycelium on phones.