I think that the best cryptocurrency wallet for BTC among software wallets is the right Electrum, because I use it and advise you, since it is very safe, but certainly not 100%, because there is no 100% security anywhere.
Bitcoin Core BitCore is the official wallet as most dealed known app to access the
BTC blockchain and store funds into it. I can't deny that electrum is also a reputable one but it still has some lacks that need to be overwhelmed by the time progress.
Cold Storage with LedgerNano or any other one, would be the safest way to keep your
BTC safe as much as possible.