I have not spent nearly as much time at Snowbird, although I did spend a little over a week there in the early 70's, and have skied there a couple of times in the last decade. The week I spent there was in March, and featured the best continuous week of powder skiing I can remember...6" to 12" of light snow every night, usually sunny days, and few people to track it all up!
Snowbird is beginner terrain "challenged". There is one fairly wide slope, "Big Emma", if I recall right, that is rated green, but would probably be rated as a black diamond or blue at most ski areas in the east. Snowbird has great expert terrain, some good intermediate terrain, but because it is lower down in Little Cottonwood canyon, which is quite narrow, the pitch averages out considerably steeper than at Alta. The bottom portion of Snowbird is best characterized by trails which funnel into the base, and get chewed up pretty quickly. The gentlist area at Snowbird is a short chair that runs back from the base towards one of the lodges.
I do not have experience with Snowbird's ski school.
Snowbird is always pushing to fill its lodges. Historically, the area has carried a high debt load, and this seems to me to influence the way they do business. My understanding is that they borrow, build, and then try to fill the facilities. I believe that the ski area company owns the Cliff Lodge. They are always offering lodging deals in the hope of getting people to ski at Snowbird. I have been in the Cliff lodge, but have never stayed there. It is a large concrete structure, designed to withstand avalanches. Aesthetically, it leaves something to be desired, but it is functional, and has amenities...shops, restaurants, etc.
There are significant advantages to staying up in the canyon, chief among them avoiding the drive up and down the canyon road. The road is often closed, usually for short periods of time, for avalanche control work (blasting the ridges above the road). Avalanche control is serious business in the canyon, and the ski patrols who do control work (blasting) at both areas are the top dogs in the employee hierarchy.
On the other hand, the drive up from the valley is not that long, and there are some good deals to be had at hotels in the Mid-Vale/Sandy area, not all that far from the bottom of the canyon road. Some of the hotels are convenient to bus routes that serve the two ski areas (as well as Big Cottonwood Canyon, with Solitude and Brighton).
There are also free buses that shuttle between Alta and Snowbird, pretty much continuously. This is the best way to get to Alta from Snowbird, because there is no way for a beginner to ski back and forth between the two areas, even though they adjoin each other. The principal connection is via Snowbird's Mineral Basin area, which is south-facing, on the back side of Snowbird. This is expert and intermediate terrain. The ridge separating Alta and Snowbird on the front side is generally precipitous. I think there are two chutes from Alta to Snowbird which are skiable, but only in good coverage, and not by anyone who is not an expert skier.
If this sounds as if I don't like Snowbird, it is only partially right. As I said, Snowbird has great expert and upper intermediate terrain, and speads out as you get above the base area. The snow is usually very good, and they do make some snow to cover high-traffic areas near the base. On the other hand, I believe that it also tries to market itself to skiers for whom it is not best suited. However, I freely confess to being an Alta snob.