Thats an intresting dillema. The pocket rocket is super soft, but judging by your height and weight, they would be fine for you. If you are only going to be doing backcounrty, i would opt for the pocket rocket. Great powder ski, ideal for backcountry hits and jumps, but if gets icy or wind packed, then its not the most powerful ski around.
If you decide to go with the XX, your still getting a solid, and in my opinion, the best mid-fat ski ever made. The only drawback too the XX is its waist(74mm vs. 90mm). The pocket has a lot more float, but the XX is quicker, more stable at speed, and more powerful overall.
Another thing to consider is snow conditions. Do you live in Utah where the snow is dry and light, and makes everyone look like a hero? Or do you live in Cali or the PNW where the snow is much heavier and wetter?
They are really two different types of skis. Hope i helped somewhat, and didn't confuse you more
: Trees are my friend