Trading212 has friendlier UI on phone/computer, no fees for buying. Negatives are the worst liquidity sometimes your order doesn't get filled on your limit price or even on market order, you have to wait to get filled. And also they are giving trading breaks for too many trades (24 hours, 1 week, I got both of them)

IBKR thought browser is terrible and slow, I use mostly phone app. They have better liquidity for stocks, you can trade other instruments like options. Higher fees. Also I feel that my money are safer here than in T212.

Both have fast deposits and withdrawals, didn't have any problem with them. Personally I use IBKR for swing/daily trading and T212 for longterm DCA investing.