Note that to drive from north lake to south, because 89 is closed at Emerald Bay in winter, it takes at least one hour. Add another 45min if going to Kirkwood. If it's snowing, add 50-100% to that.
If you're not sure and want to choose last minute, staying near Incline Village or even Carson City may not be a bad idea.
On a normal day (not a deep powder day), I'd pick Squaw first, and Kirkwood next. Then if Mott is open, as a third choice, Heavenly.
On a deep (>1ft) fresh powder day, Kirkwood - even if easy lines are tracked quickly, there's usually plenty of fresh tracks to be made. On such a day, Squaw has a line forming before I wake up :/
For lots and lots of trees (dense, sparse, steep, gentle, any variety), Heavenly.
Alpine is great by itself, but it just doesn't add anything unique (for me) compared to skiing at Squaw - other than possible crowd avoidance (which is somewhat doubtful), I'd rather ski at Squaw than Alpine any day.
Northstar, if you like groomed straight cruisers. They have decent tree skiing as well, though their slopes have less variety - the mountain is shaped such a way that the pitch of the slopes is very uniform and consistent. Compared to that, at Kirkwood and Squaw, all lines are unique in some way. BTW, on a powder day, Northstar would be my second pick - it seems that all the powder hounds like Squaw/Kirkwood/Alpine (rightfully so), and they don't come to Northstar (especially among trees in the backside).
As someone said in the thread, the best scenic slope is at Homewood - you feel like skiing into the lake. Heavenly has plenty of good view, but it's more distant. OTOH, the view from Nevada side where you can see both the lake and the Nevada plain certainly is very unique and awesome.
A friend of mine who used to race likes Mt. Rose for their steep and quality snow, but I've personally never been there.
BTW, you don't need hiking at Heavenly, if you know how to keep your speed. I can ski back and forth between Nevada and California without stopping or using poles to push. Doesn't mean I want to make that trip more than once a day, but it's not much of an overhead. That said, it's true that the connections between different areas are very confusing in Heavenly.