So, here is my 2 cents on the Steam + HTC.
First off, Steam does not care if you purchase the HTC Vive or the rift. Their business is not hardware, but selling games. If you check Steam out under the VR Game selection, you can pick what tech you have, and it will show your the compatible games. Steam would like a single standard, and all the games to support everything. They make their $$$ by taking a cut when each game is sold.
So, why VR? I believe they went to support VR because their competition is consoles. Right now Steam can offer an experience that Nintendo, Playstation, and Sony cannot. Because of that, console people will start re-considering the PC lifestyle. What is that? Steam ready PC's out of the box with controllers? WHA?!
Now... which is better? Oculus or HTC Vive?
Please note, I owned an Oculus Rift DK2 and I loved it, so it saddens me that Oculus sorta dropped the ball to HTC.
So, which is better? HTC Vive, and here is why...
With the announcements and price of the Oculus Controllers, the price of the HTC Vive and Oculus Rift are equal. EXCEPT that you need to purchase an additional camera to get room-scape with the Oculus. (see news on Toms Hardware page.)
Then you take that Oculus is trying to be a little proprietary with their games, where Steam has a giant sign that says, "Everybody Welcome", and I can't with good conscious advise anybody to the rift. I just haven't heard what the Rift provides that the vive does not. (aside from build in headphones, which I don't find compelling.)
So yeah... make your decision.
I own a HTC Vive, and I still use it about twice a week or more. (Rec room is pretty fun.)