I stayed in Plagne Soleil with a group of 11 last year and I'm afraid to say it was the worst Apres Ski I've experinced in 6 seasons.
Even when we ventured into Plagne Centre it got no better.
By Apres Ski I mean a large selection of bars to "crawl" around eventually ending in some pub/club with a dance floor until 1 or 2am. If this isn't what you're looking for then Plagne Centre might be ok, although I also thought the choice of restaurants was disappointing.
By the sounds of a few of the other replies I'd head lower to Bellecote or 1800.
