I'm not too sure about achiever....but TopScore is a really good simulation of the actual test. The concepts are slightly harder on TopScore so if you understand them all you should do really well on the real test. I think it simplifies the reading section quite a bit. I did better overall on the real test (19, 19, 20) than my 3 practice tests (mostly 17's and 18's).
AcetheDat is absolutely terrible. The QR is too easy, the RC questions are shallow and unchallenging, PAT is too hard, and there are errors in the Sciences. It also has to be taken while online. I would recommend it as a last resort only after you've exhausted every other practice test, question set, review book, and textbook out there.
