Ok, so, the display it comes with:
Low persistence AMOLED at 1920x1080p resolution, using MIPI interface.
Using the MIPI interface is the real advantage here, as we can stick in any old 2560x1440 AMOLED display and it will work with no modification's.
I see that some people are working on a 3840x2160 display interface, I guess the interface is the same, but the control board that comes with the OSVR doesn't have the required bandwidth, having a "class 2" chip, when a "class 1" chip is needed. The other issue's with upgrading it to 4k are two fold, HDMI 1.4 does not support 4k, you need either HDMI 2.0 or Displayport, secondly, hardware will be pushed at 4k in VR.
Advantages I have found for the OSVR so far:
OSVR doesn't use software for distortion, and uses a different type of lense than the rift, reducing required processing resources.
It appears that they can't legally claim this; but the head tracking looks exactly the same as the Oculus Rift. If I had to venture a guess, I bet you can even stack your camera's. Also, the box in the back allow's for 360 degree tracking, with backup sensor's on board.
Disadvantage: (so far)
They are making a claim that there is something special about their stock display that is unclear as of yet, but it appear's to run at 60Hz. They list it is as "60fps", which I am assuming is the refresh rate. But apparently the display run's fine at 60Hz, I am a little skeptical, but only because I know how crappy my Oculus looks at 60Hz...
*edit* The factory display is a 120Hz panel, but the hardware runs it at 60Hz, leaving room for future optimization, or overclocking.