I used both the GMATPrep Software as well as Veritas Prep
for my studying and found the questions on Veritas
to be a little bit more difficult than some on GMATPrep. But, with that said, I think the Veritas
tests are a great tool and will help you learn from your mistakes and score higher over time.
Since nobody actually knows the GMAC algorithm for scoring, all of the tests you take will NOT be perfect representations. However, people tend to think of the GMATPrep as the "most accurate" since it is developed by GMAC and likely contains the most similar algorithm to what it on the actual exam.
In terms of price, I believe the Veritas
exams are $49 for 6 exams (free if you sign up for a class with them) and GMATPrep gives you 2 exams free with the software and then you can buy 2 additional exams for $50. I think both are a wise investment assuming you have the time to take practice exams.
If you are just starting your studying, I wouldn't look too much into the scores. Try to focus on areas that you are weak in and make sure you master the concepts (learning from your mistakes is the most important part of GMAT studying) and make sure that you make each test as realistic as possible (e.g. full length exam with AWA and IR sections). This way when you go to the test center on test day you will have the stamina to sit there for 4 hours straight.
My GMAT Story: 710 to 760