GMAT Club test are better than other practices tests I've tried so far. GMAT club tests have very detailed explanations for questions and also provide the information about your performance for each section, which helps me identify my weakness. Another thing I like GMAT club tests is that I could make marks if I guess several questions during the test. GMATClub is a great source for questions that are at par with the actual test. The discussions on the forum are very useful. When you go through the entire discussion, you get to know the other perspectives and methodologies for each question type.