The GMAT prep tests are by far the most like the real test, as they are written by the same people as the actual test.
The one you've taken is probably the best one to have taken before class begins. (It's the one we usually recommend.)
The other tests all have their strengths and weaknesses, but all are good practice for the real exam, though none of the scores will be quite as accurate as the GMAT Prep test. For this reason, we recommend saving the other GMAT prep exam until the end of the course, just before you go in for your real exam.