ya ive been to both of those. powder mtn is like this secluded place where you get a lot of untracked powder. not really steep tho. but if you dont care about that, and just want the powder its great. i hear you can go there 2 weeks after a big storm and still get fresh powder.
snowbasin on the other hand, its super fancy from the olymics and pretty steep too. i love it there. after Alta and snowbird in my book...comes snowbasin. its alittle more crowded than powder mtn, but still great terrain and not crowded becaues its likes an "unknown" place.
ps: powder moutain has great "backcountry" going down to the access road with a shuttle picking u up on the side of the road.