All depends on what you want to do with your board. At your weight, 151 might be a bit to the long side for you if you are just doing park. When you like to ride the groomers fast too, you should get that 151.
That 151 will last longer for you as you are still gaining weight and are growing, and you'll be able to do park with it too. It's quite a bit of a gap between your old board though...