[TheSmitty]

This is not exhaustive but just some observations....

So as has been mentioned Woot has refurbished Voyages' on sale for $69, so I bought one for giggles and grins.
I now have a Oasis 2 (with original half-back leather cover), Paperwhite (2018) and the Voyage. I will give at least one away to a family member soon.
Anyway, here are some of my observations. First, I love the bigger screen and design of the Oasis 2 above the others. It is still my go to reader. Switch back and forth between my hands is just easy and intuitive. More words to have eyes on means a little less flipping for me.
The paperwhite is nice but is thicker than either of the others and a little taller than the Voyage. What I don't like is touching the screen to flip pages. I guess my skin is more oily than most but it gets dirty pretty quick. I have the same problem with my iPads of course.
The Voyage is the newest edition and I have only used it for a few days but here is what I have noticed and experienced thus far. The display is different than either the Oasis 2 or the Paperwhite. The background is a little lighter and the text appears to be a little darker but let me quickly state that this could because of the lighter background. I do not think this is better and is not something I would have noticed had I not been clued in to look for a difference.
The other thing I noticed is that the Voyage is lit at a very low level even if you think you have turned the light off. I am not sure why this is as neither the Oasis 2 or Paperwhite do this. When their light is off they are dark. I tested this in a dark room. This low lighting could also be part of the reason the background on Voyage looks lighter and text a tad darker.
Lighting wise, they all work just fine. I typically do not read in a pitch dark room, rather I will read in a low light room and have to use the lights a bit. They all seem fine to me and I have not bothered to look for gradients etc.
Lastly with the voyage, I do like the touch controls but it took a bit for me to get used to them. In the end I prefer the physical buttons of the Oasis 2.
I certainly will be keeping my Oasis 2 (I love the case by the way) and I will keep my Voyage (its' nude, I just store in a sleeve). The paperwhite would be just fine if I didn't have other devices but it will be the one I will be gifting to someone in the family.