The Jupiter reporting station is somewhat suspect from some comments I've heard.
The Targhee to Jackson dropoff in snowfall (463 vs. 366 both midmountain) is not nearly as drastic as the LCC/BCC to Park City dropoff (461 Snowbird base vs. 287 Summit House).
But the altitude impact is more than admin suggests. Alta and Snowbird are both as wide at the top as at the base. So there is roughtly an equal amount of skiable terrain above and below midmountain (~9,500 in both cases). Jackson is a peak at the top of Rendezvous, and very wide at the base, with a separate mountain Apres Vous that only goes a bit more than halfway up. So I would say there is probably 3x as much terrain below mid-mountain (~8,400) at Jackson as above. As an aside, measuring snowfall at 11,000 on Vail is OK by me because it has much more terrain high up than near its base.
Due to the layout description above, I recommend focusing on Jackson's mid (480 this year) rather than upper mountain (606) quote for snowfall. The mid-mountain data set also goes back to 1971 and thus is very useful as a comparison for what kind of season they are having. While press releases are just going to quote that upper number, the season-to-date mid-mountain number is always shown on their report page
http://www.jacksonhole.com/weather.snow.report.asp and I give Jackson credit for that.
But as rfarren points out, the key issue with Jackson is exposure. The refrozen coral reef is most unpleasant, but I can tell you that the warm days are not very good off the groomed. All that low-density terrain on the lower faces that is so good for powder is unconsolidated goo on a typical sunny March day. Think the Mineral Basin liftline, but 2,500 feet lower.
The SLC locals are within drive distance, so they do have the opportunity to cherry-pick Jackson's weather. And with its terrain quality I would think that would be worth doing once in a while. As I've mentioned before Jackson rates #8 in North America IMHO, but if you rotated the mountain 90 degrees so that it faced NE instead of SE it would jump to #3.