7 Springs gets significantly less natural than Timberline: 105 vs. 150 inches. However, natural snow is more myth than reality in the Mid-Atlantic due to its highly ephemeral nature. Unlike the West or the Alps, where natural powder can stay dry and fresh for many, many days, the Mid-Atlantic's cruel and relentless freeze thaw cycles generally dash anyone's hopes of fresh powder 1-2 days after a snowfall. If you are lucky (as I have been on a few rare and truly blessed occasions), you might arrive during or just after a dump, but those chances are unlikely. Hence, I always tell people to look for resorts that frequently re-coat with manmade snow (7 Springs, Snowshoe, and Whitetail are good in this regard). I also like the resorts west of the Allegheny Front b/c they generally can sustain better bases for longer periods of time and have less nasty freeze/thaw cycles than those east of the line.
Because skiing is limited in the Mid-Atlantic and supply is high, all resorts mentioned get kind of crowded and expensive during weekends--especially January. You'll get cheaper slopeside at Timberline, where I own a small condo, but the lifts SUCK. Saturday crowds in January and February are taxing Timberline's old, slow lifts to the max. With stoppages, its not unusual to spend 15-20 minutes riding a lift and another 15-20 minutes in line. On saturdays, I usually ski 0800-1000, break from 1000-1400, and then ski the later in the afternoon. Sundays, however, are better, and midweek is ALMOST HEAVEN.
7 Springs gets crowded as welll, but crowds spread out better there on weekends. If you know where to go and I ain't telling, you can generally find an uncrowded lift, even on big weekends. Also, if Bob Dupstat does get his high-speed installed on the North Face, that will really do wonders for the place by eliminating one of the biggest weekend bottlenecks.
The other strengths of 7 Springs are its food services, ski school, grooming, rental fleets, and off-slope activity.
For true experts, Timberline's out of bounds and its double black terrain is definitely a cut above what 7 Springs has to offer, especially after a dump. Only Blue Knob rivals Timberline in this regard--especially out of bounds. The two mile long Salamander Trail at Timberline is also good for beginners. But I kind of like 7 Springs for intermediate terrain--especially the black trails on the North Face (they should really be marked blue).
Well, my wife's favorite Mid-Atlantic resort is 7 Springs. I like Timberline. You'll have to make up your mind and do what's best for your group. Enjoy.