i'm your exact height and weight... i've got a 151, 153 , and a 155. the 155 is definitely my favorite, even in the park (and i'm riding at bear so i'm mostly jibbing). but it's basically just as maneuverable as the 51 and 53 but its definately more stable.

Well in this case it all depends on what you plan to focus on when youre in the park. a smaller board for the most part, like a 152 will provide you with lots of flex and make your board very manipulatable, which is good for jibbing. however what you gain in flex and manipulation you lose in control and over all stability, which is key for jumps. having some stiffness will save you on those sketchy airs. you mentioned pow and being your size and riding a 152 will probably leave you in trouble in powder and high speed turns. i think it may be a better idea for you to look at the 154-157 range, besides many pros about your size (ie scotty lago) ride that size.

my recommendations if you want to go small and get some bigger performance:
K2 - WWW, its got a lot more effective edge for its size (a 152 rides like a 156), thus giving you the best of both worlds
Atomic - pivot, same deal as WWW, but not as much difference, plus its got rail protection in the base