CT-Art versus PCT
Tacticus Maximus has a post explaining why he prefers Personal Chess Trainer to CT-Art. I have been planning a post arguing the opposite, but it can now basically be seen in his comments. Note in that comment I mention the 5x5 board in CT-Art. For those who don't know, when you get the answer wrong twice, a 5x5 board pops up with a tactical problem containing the same theme as the original problem. Once you solve the problem in miniature, you are sent back to the original. Ultra cool.