Pete, I skied in Mammoth for 20+ years. Unless they get a lot of fresh snow, you'll be skiing mostly groomers or crud as they have a big skier population and they ski it out pretty quick. Any thing left will set up to sierra cement, it's heavy coming off the Pacific with a lot of water content. Having said that, California is supposed to get some storms this week, and when it dumps there, it really dumps. Eight or more inches overnight is the norm. It's just not going to be as light as it is in Idaho, and that's the main difference. Their website says they have 15 feet of base at the top, so coverage is good.
The trees are tight there. On the other hand they have a lot of open bowls, steeps and huge groomers. It's going to be mostly on piste, but pretty steep and wide open. You'll definitely want to hold an edge. It's a big place, but even with 28 lifts it can get crowded on weekends. 45 minute liftlines are not that uncommon on the busiest days (which you probably won't get this late in the season), but midweek they do a good job of dispersing the crowds so you don't see it.
My best advice is to see the conditions once you get there and judge accordingly. There will probably be a lot of new snow, but it will be heavier than the Rockies.
BTW, it's high up there. I think the town is about 7,500 feet. The mountain tops out at 11,000+ and the air can get a little thin. My favorite runs off the face were Scotty's and Dave's. Enjoy!