Does getting an MS make you a more competitive PhD program applicant?

If your undergraduate degree is not in computing, or if there are gaps in your computing coursework, additional courses taken in pursuit of an MS degree could help make your PhD application more competitive. Similarly, if you did not do research as an undergraduate, or if your research did not lead to publications, research experience gained as an MS student could strengthen your application.

However, having an MS can also raise expectations.  While a lack of research experience is easier to overlook in an undergraduate applicant, it is more worrisome in an MS applicant, because they likely had opportunities to do research but did not pursue them.

In general, if you have decent grades in computing-related discipline, and your goal is to earn a Ph.D., you should apply to Ph.D. programs.  You could apply to MS programs as well as a backup path to polishing your resume before applying to Ph.D. programs again later.