For gaming ZF9 is best with an input lag of only 21ms. I've owned the Q9FN as well just so you know. It even beats all the QLEDS as they flicker their backlight at a lowly 120hz (480hz in movie mode) regardless of the frame rate of the input/source, this leads to a lot of image duplication when gaming and makes you see edges and thin lines while panning a camera being duplicated and they flicker a lot as well, especially in games that don't use motion blur on objects and camera movement. If I rotate the camera around in Spiderman PS4 the sky scrapers looks quite bad on the Samsungs. Sony on the other hand flicker at 720hz this makes 30fps games like Spiderman look much more stable when panning the camera and you don't get image duplication.
Sony ZD9 is best for critical movie watching and a center seating position (poor viewing angles). It's not an amazing gaming TV as input lag is 24.5ms in 4K and 40ms in all other resolutions.
OLEDS have amazing picture quality but run the risk of image burn in. If you use high brightness and play Zelda BoTW for ~100 hours, the red hears will wear down the organic LEDs, then you may get burnt in dark cyan harts as a result. If you vary your content and don't grind one game with a lot of saturated reds and don't use high brightness it could very well be the best option. But ZD9, ZF9 and Q9FN will procure brighter and more vibrant HDR images if the content is mastered above 1000 nits. This is very apparent in gaming.
The only down side to ZF9 is that is suffers form a bit of blooming in HDR with dark scenes and bright lights. Here Q9FN wins but in all other aspects ZF9 wins, the image is much cleaner and no details are lost or darkened to Samsungs overly aggressive dimming.
Price is of course important. If you can get a Q9FN for a considerably low price it may be worth it, but is suffers form screen uniform and banding in dark content.
I personally went with ZF9 over Q9FN and Q900 due to a combination of Sony's over all higher image and motion quality as for the price I paid, and I'm okay with the slight blooming as it out performs anything else for gaming and top image and HDR quality in my eyes.
Finally ZF9 UI is very responsive, no complaints at all.