Just a quick link to an interesting article in Massively, where the long argument between Free2Play and subscription based business model is reduced to a few simple numbers: Revenue from subscription for MMOs went down by 5% from 2009 to 2010, while Free2Play revenue went up 24%. Nevertheless the subscription model is still ahead, with $1.58 billion annual revenue versus $1.13 for Free2Play.
Note that this is revenue, not profit. I don't have any numbers, but I'd like to point out that in a subscription game everybody or nearly everybody pays, while a Free2Play game has to carry up to 98% of freeloaders, which *do* have some cost. Thus I believe that subscription games have a better profit margin.