Hello Li Mei Lin,
Personally, I used the PM Exam Simulator. Like Craig, I found it realistic and appreciated the significant number of full exams. It worked very well for me, and I also give it a high recommendation.
I did not feel the need to do multiple different full exam simulators. Instead, I used the PM Prepcast, and Rita Mulchay's PMP Exam Prep book. Both of those had sets of questions at the end of each chapter or segment. I found these shorter question sets (typically about 25 questions after each chapter) to be quite helpful when studying each specific topic. When it came time to practice doing a full exam, the PM Exam Simulator did a very good job for me, and I did not feel the need to try any other simulators in order to feel ready for the test.
Good luck!