By definition, maintaining Flex is "sufficient power" to climb away... However, that might require a high degree of flying accuracy, with any degradation leading to unsatisfactory airspeed / RoC.
That said, selecting TOGA from a stable climb out will destablise the situation somewhat...
Personally, I will leave Flex, and see how it goes. If either I or my colleague (I brief the P2 to feel free to state/call TOGA) are unhappy with the perforrmance, I will then go for TOGA.
In a lightweight / high V speeds situation, keeping Flex slows everything down nicely
NoD