Not all the mobile wallets are considered less secure but majority of the wallets are! Wallets like mycelium are trustworthy in the sense you can use them for spending your small amount of bitcoins. I have been using mycelium for quite a long time as a mobile wallet for spending my funds immediately when I am away from my PC. But on the other hand, you shouldn't be having large chunks of bitcoin in mobile wallets, web wallets or hot wallets. Hot wallets and Web wallets are some of the bad wallets which one can trust upon as they have poor security when compared with mobile and desktop wallets.

I would suggest you to have a hardware wallet like Ledger/Trezor for holding your btc for longer term and electrum as a desktop wallet connected with Ledger and mycelium in your mobile. Electrum mobile wallet is certainly bad at times and they could create problems at times. Here is a post of mine about the disadvantages of using a Electrum mobile wallet over another mobile wallet like mycelium : Bitcoin account my mobile


Fingerprint/Pin alone wouldn't make a wallet secure as far as mobile wallets are concerned. Your mobile would always be connected to internet which might pose a problem for you if your mobile is affected by a malware. Consider like the hacker has injected a malware in your mobile, and when you send btc it might redirect to his address.You should always use wallets like Electrum in a offline computer or a hardware wallet for storing large amounts.