Hi, I've been in hr for 13 years. I was "over confident" and took the SPHR and failed. I then took a class and decided to go for my PHR, and passed. The study material for both are the same. The SPHR places more of an emphasis on stategy. The SPHR is about applying the "terms" you learn, and not just rote memory, which is what the PHR is about. Deciding which exam to take was hard for me, and now that I passed the PHR I wish I went for my SPHR.
I used the HRCI study material, and it worked perfectly. There are six modules, and each comes with flash cards. If you read all the modules, and study, you will pass.
If you've been in hr, at an exempt level for 5 plus years than you may want to consider the SPHR.
Good luck, Maggie.