Personally, the only reason I would recommend Electrum over that of Bitcoin Core, is because its a lightweight client. If you don't need a lightweight client, i.e you don't wish to keep a copy of the Blockchain on your device, then Electrum is the best choice. Otherwise, go with Bitcoin Core.

I would also recommend against using any wallet, on a phone. Especially, one that you connect to the internet with regularly, and download apps on. Phones, are a little bit more difficult to secure due to their operating system, and the way the general user uses them.