Which is better - chess.com Tactics Trainer or Chess Tactics Server ?

I like this site, as it is very easy to use and quite modern. I wonder if I would gain the same or better benefit from the tactics training on this site, as opposed to the Chess Tactics Server at chess.emrald.net. I am registered at both places, but here only as a free member. Any suggestions ?

I am a user of both servers, here I have about 11 000 problems solved, at CTS I have about 22 000. There is a difference between them: the tactics trainer here ussually focuses on problems with longer thinking times, while CTS main goal is to train lightning reactions. Here for instance you will find many studies involving stalemate or underpromotion, requiring an average thinking time of let's say 5 minutes. Both tactics trainers are very good and my opinion is that they complement each other.