Snowboard Size Question for Park!?

Hello people. My name is Tyler and i need your opinion on the right snowboard size to buy for park. I am 5 6" and currently i own a 150 forum manual. After working at camp woodward east using the roller boards (which are like a 136 or something like that) I feel like i would have alot more control on spinning faster and flipping faster If i buy a 140 cm board. Should I buy a 140 cm?? would i flip and spin even easier in park off jumps and rails? Yeah im notta scrub i compete with usasa so i need to go bigger and bigger spins and more flips. so pleasee help :D