I just start at gccg, but i think it´s a way ahead of sda (which i have been playing for more time). One good thing of it is that you can talk directly with the programers to make suggestions of improvement, and it´s likely you will be heard.
I didn´t experience bug problems (drop-out in the middle of a game) like a had on sda, at least until now. And i like the chat and the possibility of just watch the games. I think it´s a nice plataform to run some kind of online tournament.
For all that and some things more i have to go with GCCG!