This is like the story of the blind men and the elephant, because each has his or her own in-the-trees "happy place" in the mind's eye, and it's different for each of us depending on a bunch of stuff. A Sunday River skier may be thinking of open hardwoods with no wintertime canopy, like Last Tango or Blind Ambition. This may look somewhat like some of the "sugar bush" (as in sap collecting, not necessarily the namesake ski resort) runs I've seen in Vermont. Usually these are at relatively low elevation and may depend on exposure. Pretty sure I tend to see more evergreens on north-facing slopes and hardwoods elsewhere.
One common denominator, I think, is that in the Rockies (but perhaps not in the PNW), generally, trees get plenty of sun but strive for moisture, thinking on a year-round basis. On the other hand, in New England it tends to be the opposite: plenty of moisture and not enough sun. (Anyone who's ever done any hiking in the higher mountains of the northeast in summer can tell you that. Between thin topsoil, cool temperatures, generous precipitation, and frequent cloud cover, the ground tends to be sopping wet above 3,000 feet pretty much all year round, when it's not frozen.) These patterns affects growth habit. Other factors include history of burning and/or logging.
At Saddleback there is not much in the way of "natural" tree skiing. The conifers are simply too dense. At these higher north-facing elevations they tend to grow in a bonsai-like way, stunted by fierce winds and heavy loads of snow and ice for five or six months of the year. Everything becomes condensed and scaled down, including the space between trees. For this reason, glades more or less have to be human-cut. Thus much of the gladed terrain DOES look like "a field of telephone poles," albeit rather thin and spiky ones, often with a dense canopy of needles and snow just overhead. The canopy can be so impenetrable at times that on a sunny day it can seem very dark. Because humans have to take out many many trees and branches to make even a barely skiable run, glades tend to be tight for the very simple reason that it takes a hell of a lot more work to make an open glade than a tight glade. A secondary reason is that the snow tends to stick and to stay much better if the slope is not opened up too much. A consequence of the heavily glaciated topography and very thin soil is that there also tend to be a lot of big rocks, logs, stumps, and etc. underfoot, that require a significant base to cover. Over time glades tend to open up a bit because the folks who got royally sick of cutting trees last year eventually regain a bit of motivation during the season and go back to cut out some of the worst offenders the next fall.
This is informative. Thanks for putting this together for those who don't know.