The advantage and disadvantage of Valve's VR is entirely that it is tethered to a PC (at least wirelessly if you have the wireless module) and the PC ecosystem. That means you can take advantage of your existing Steam investment, Steam sales, and interface.
The disadvantage is that maintaining a gaming PC seems daunting for some folks. Also, you have to figure out how to get cables from your PC to an empty space that is wired for VR. That can be a logistics problem if your gaming PC isn't near your living space.
I've had the opportunity to use headsets from both companies, and own a Vive.
Oculus' devices seem generally a bit lighter and more comfortable, and Valve/HTC's devices tend to be a bit heavier, but with more focus on high-end performance.
This varies across their product lines of course, but I think it's fair to say both are strong contenders for good consumer VR products, albeit with different primary focuses.
