It appears the main improvement is the resolution but it's difficult for me to get a sense of how important this is without having used a Paperwhite.
The biggest factor, I think, is whether you want buttons for page turning or not. If you get a Paperwhite, the only way to turn the page is to tap (or swipe) the screen. If you get the Voyage that'll still work, but there are now sensors on the edge as well with some sort of haptic feedback.
If neither of these things sound important to you, get the Paperwhite and save $100. It's a great e-reader.
Apart from the resolution upgrade, the changes on the the Voyage seem a bit of disappointment to me to be honest.
The higher DPI should be an upgrade to the Paperwhite and the page turn buttons are unnecessary. I thought I missed them when I upgraded from a Kindle 3 to the Paperwhite but touching the screen became natural after using it for a short time. The flush bezel is nice but no big deal and I leave the light on my Paperwhite at 100% all the time, so I don't want it to 'Adapt'.