I like the larger screen size on the Oasis, but I didn't think the Oasis 2 had that much better of a screen, compared to my Paperwhite; aside from the size.
They both have the same PPI; and the contrast levels are only marginally better on the Oasis 2.
On a different note, the older Paperwhites, with 212PPI screens, can be gotten for as low as $51 (half the price of a 300PPI Paperwhite) on Amazon here:
https://www.amazon.com/gp/offer-listing/B00JG8GOWU/
It's actually a great deal if your eyes aren't the best anymore, and you can't see the difference between 300PPI and 212PPI anyway.