If you can get both then that will be better, the usual setup is a SSD for the OS and applications that you use the most, and a HDD for data.
Ditto, this pretty much mirrors the ideal setup these days. Responsiveness and overall speed of JUST an SSD for your OS drive instead of an HDD will be felt without a doubt on even some of the oldest computers.
With Piledriver so close, it can't hurt to wait and see what level it performs at. Maybe that bang-for-the-buck factor will really come back into focus for this architecture.