The guys in the Lab have lived out there for years and there is no real perfect balance. For powder it's Alta/Bird no question. They average 500" a year where the park city side only averages 360" - thats over 12 more feet of snow at Alta/Bird. But the catch is no park. (bird has one but not really) So the answer to the other half of the question is Park City for park/pipe. It hosted the olympic qualifier for pipe this past season so 22 ft walls for sure. and the jumps are money, so big you can almost see them from space. Only one true answer - live in SLC and get passes at both. When high pressure kicks in head to PC - when it's nukin snow head to the LLC.
-The Lab