I have a Voyage and I bought the Paperwhite 4 about a week after it became available. Both are 3G. They're about the same weight. The Voyage is smaller but not a lot. I always liked it's smaller size but I found myself accidentally turning pages with the flush bezel so I read on my Paperwhite 3 a lot more than on the Voyage.
The Paperwhite 4 also has a flush bezel but for some reason I'm not always turning pages if I hold it wrong. Maybe it's the size or something about the shape.
When I put the Voyage and the Paperwhite 4 side by side the Voyage screen seems better but so does the screen on my Paperwhite 3. The difference isn't something I can put my finger on but comparing them it's there. When I'm reading on the Paperwhite 4 the screen is perfect. I've learned to accept the fact that it doesn't compare well given that it reads so very well, and that's why I bought it.
I was so pleased that I bought a Wifi one as well. Then when they went on sale again I went crazy and bought another one. I'm sure I'm bound for the looney bin but the truth is I wish they'd go on sale again.
When I put the Paperwhites side by side they're all very different. Some look as good as the Voyage. Some don't. Reading on them they're all perfect.
Last week I offered my Voyage to my sister, who listens to audiobooks but is wondering if she wants to go back to reading visually. So far she hasn't accepted it but she may. She can't have my Paperwhite 4's.
The more I use these things the more I realize how good they are to read on. The only thing I don't like is the power saver feature that makes me wait about 10 seconds before I can start reading if it's been sleeping a while. I can turn that feature off but I want to be kind to my battery so I put up with it. Other than that it's easily my favorite reader.
I've been using one of them without a case but I just put it back in it's case and started using my Paperwhite 3 out of it's case. I like having one device without a case by my bed. I've often done that over the years and I've never damaged one yet. Now that I said that it'll probably happen tomorrow.
The Voyage does have the Page Press, which I never remember to use, and the self-adjusting light which I keep turned off. So to me the Voyage is just a smaller Paperwhite. I'm finding the Paperwhite 4 the most comfortable to read on.
Another thing that I always notice when I compare devices is that even within the same model the screens are all different; as different as from model to model. I keep hearing how the Voyage screen is better and mine is very good but some of my Paperwhite 4's and one of my Paperwhite 3 screens are as good. I think personally it's just the luck of the draw.
Barry