Is the certificate any different for students who work the Hacker Edition problem sets?
You must do the standard problem sets to get a certificate; Hacker Edition problem sets are completely optional and have no effect on grading or certificates in edX.
The CS50x 2014 syllabus covers this question in the section on Problem Sets:
Both editions essentially cover the same material. But the Hacker Edition typically presents that material from a more technical angle and poses more sophisticated questions. To receive an honor code certificate from HarvardX, you must submit the standard editions of problem sets. But you are welcome to do the Hacker Editions for your own edification; it just won't be possible to submit Hacker Editions for credit (or extra credit).