Regarding android wallets, i've never had any issues. I've been using them since i started dealing with cryptocurrencies, and everything has always been in its place. My friend, who is a serious trader, initially used Electrum for many years and later switched to a Trezor One (hardware) wallet. There is always a risk of hacking attacks, you never know, but i think android wallets do a good job, although i also believe that opting for a hardware wallet is a better choice.