I'm leaning toward CramMaster, because it provides instructional material if you don't know the answer, and it is adaptive in that it focuses the training on what you don't yet know. But I've also heard that Transcender is the best in the industry. Do you have an opinion on which product I should use (feel free to recommend another product if you think it is better than the two I am looking at)?
I have trouble providing recommendations for practice tests for people because I create these kinds of materials on contract for other vendors, and I don't know enough about your background to understand your specific needs or what other materials you have to prepare for your exams. Therefore, my advice is to follow your own instincts, but in a limited way at first. In other words, try one of the ExamForce products (say, perhaps for exam 70-218) and take that exam. If you pass and are happy with your experiences with the product, you won't need anybody else's recommendation to decide what to do next. If you're not happy or don't pass, try an alternative product, repeat, and see if you like those results better. Repeat as needed, until satisfied or until you get your MCSA!
I hope that helps, and good luck with your exams.
This was first published in July 2003