Well like all TRice's, there is a different in nose shape between his smaller boards and the larger once. You say you are stuck between a 159 and 162, but they don't carry either of those sizes, so I'm going to assume you mean the 157 and the 161.5.
The 157 and lower TRice boards normally have a park/jib-specific blunt nose and tail compared to the 161.5 and up that have a more pow-specific pointy nose and tail. Other than that and the flex ratings for each size they are much alike. You said you ride pow at times. I'm not sure how frequent that may be, but just based on the fact that you ride pow and aren't very park oriented I'd go for the 161.5. I just recently bought a 161.5 TRice Limited Art of Flight edition. I haven't taken it out yet, but love the look of the board and just strapping in for some carpet sessions love the way it feels.
BTW, we are the same height but your about 10 lbs more than me so the 161.5 is more ideal for our size. If you wanted to start hitting the park, look to maybe get the TRice Pro and another park board, thats what I'm doing. They are normally pretty cheap. From what I've heard the 161.5 will be fine in the park as long as your not going nuts on rails and all that, but would you honestly want to put such a beautiful board through rail and jib runs? I'm not. lol