Not sure what size snowboard to get?

I'm mostly into freesstyle so im worried i might get a board to big and then not be able to work with it. Im 5"11and about 150 pounds... im looking at getting a new stepchild board and im either gonna get the 152 or 155. I feel like i should be riding a 154 so im not sure what to go for. Im open to any suggestions. Also i have size 10.5 boots does that mean i should be riding a wide board or is that 12 and up???