Between the three, it depends on a few factors. I can't speak for the PSVR as I haven't tried it (I hear it's the most comfortable).
I find the rift more comfortable than the vive as the vive feels front heavy (I notice it when moving my head quickly), and I really like the touch controllers compared to the giant wands of the vive. For room scale, the vive pips the rift, but with the additional sensor that comes with the touch controllers the tracking has been flawless on the rift (I do wish there was an easy way to wall mount them like there is with the vive sensors though).
Yes, there are titles that are platform exclusive, but in general the majority will support both by using the open VR standard. Steam allows you to filter VR titles by headset so you can have a look yourself to get a feel for how many titles are or aren't exclusive.
With regards to your hardware, you're going to find that your 290 will struggle a bit in some titles (like elite dangerous, which can be somewhat demanding in 2d, let alone VR). Remember, you're trying to maintain 90fps on 2x 1080p screens. I run a 980ti and that is fine though. Multi gpu does not currently work for VR so think single cards if you want to upgrade.