The CSCS is historically the most recognized certification in the strength and conditioning field; although, obtaining it is as simple as passing a rather long multiple choice test (unless they've changed it since I took it over a decade ago). The thing to consider is that you must have at least a bachelor's degree to obtain this certification. The NSCA will let you sit for the exam in your last year of college, but you will not become CSCS until you pass the exam and provide proof of graduation.
What is your career goal?
Overall, I would recommend that you obtain the CSCS if you desire to be a strength coach at the collegiate level or above, as this is generally considered a requirement to even apply for these types of jobs. However, previous experience is as important, if not more important, than a certification.
I'm not familiar with the NASM-PES as this organization was not in existence when I obtained my certs.