softer flex is better in park usually. They just really butter off lips and it's easier to spin off lips. You can butter easier off lips, which helps initiate spins. Stiff skis work well in park too though, it just takes some getting used to. Stiff skis are better all mtn, they dont wash out in the tails and if you ever get into any crud snow, you won't eat shit and die because your skis wont get squirly.
Try skiing park with some stiff skis and then switch to some softies and it will be some much easier. I recommend getting a set of both stiff and soft skis.