1. Why do you need a statistical software? Main purpose?
If you are just a college student and you'll just be using the software for the basic statistics course, then you might not need to buy expensive licenses (yes they are very costly), there are a lot of free online statistical calculators that one can use for simple statistical analysis. Of course, it would be a different story, if you have a statistical consulting firm, you might need more than one statistical software since each software has their own unique tools for different situations. In the academics, SAS, SPSS, and STATA are very well accepted and recognized. In the pharmaceutical industry, in some countries such as the Philippines, they require SAS for clinical trials.
2. Who is the end-user?
Some softwares may require additional training for new users. SAS is a software that is heavy on programming, while SPSS has an interface that is more user-friendly.
3. Budget?
I think, SAS License is the most expensive of the three (at least here in the Philippines), followed by SPSS, and then STATA.
If there is no budget at all, and one is in health research -- then EPI-INFO or OPEN-EPI is the best option. They are actually freewares :)
Link for EPI-INFO: http://www.cdc.gov/EpiInfo/
Link for OPEN-EPI: http://www.openepi.com/Menu/OpenEpiMenu.htm
