I use both platforms. I prefer Freetrade app in terms of design. I also prefer their customer service and the fact they are a British startup.
T212 have more functionality - A web platform, fractional shares (coming to FT soon), a free ISA account. They also have a range or order types including a limit order which routes Direct to Market which means that you can buy on the bid and sell on the ask. I’ve made some decent gains using limit orders in this way especially with shares with a large spread.
T212 are also about to launch Autoinvest which automate trading.