I've done at least 3 from each of those companies that you have Practice Exams from. I've learned something from each and every exam that I'm up to so far (up to my 16th at the moment). There's been a couple that have mistakes, TSSM as sam stated had a mistake, and one of the Compak ones had a mistake. But everyone makes mistakes, so it wasn't a big deal for me.
I think that if you learn at least one thing from each practice exam you do, which can be a very simple thing, then you have done well. With the questions you get wrong, do them again and see how you go. That's how you will learn from practice exams. Not attacking you, but just giving advice. If you get something wrong, find out why and what the correct method was to do it, and then do it again yourself. Don't look at the solutions and then say "oh yeah, won't make that mistake again". Trust me, it helps if you do it again.

Going back to your question, all of them are useful. If you can, get a hold of the Compak and QATS ones. In comparison with the past VCAA Exams, I find them fairly close in terms of difficulty.