I just did a week in Tahoe and spent 2 days each at Heavenly, Northstar and Kirkwood. Kirkwood and Northstar were the best like others have said but it was nice to stay in South Lake and have alot of food/entertainment options at night. We had a car so it was a short hour drive to either Northstar and Kirkwood when we went there. Kirkwood's village is very small but that is also the appeal to it as well as it is not as commercialized as other places.
If you wont have a car and are staying in South Lake you can check out TahoeSkiShuttle.com and they have shuttles a few days a week from South Lake to Northstar and kirkwood for $15 a person roundtrip.
If you get to Kirkwood, definitely ride the wall, its an experience of its own.
I'm going back to Tahoe the last week in Febuary and Cant Wait!!!!