Cambered faces allow you to run the ball off the near-edge ie through third-man etc . They are more durable . When i hit a ball out of the centre with a cambered bat it just feels like the convex shape is making the shot feel sweeter in the hands , not pingier ...but it feels pingier . But flat face gives better feedback ie ball always tend to go where you think it will . For whatever reason , my favourite bats pickup wise are all cambered . But my favourite 'weapon' bats are all flat faced .
Ultimately, not that much difference. ...if the flat face bat feels better and you're prepared to bone/knock in edges more (and possibly do a touch more run in repairs) then just go with that bat .