I think the only real boon for the Oasis is the better screen resolution
The current Paperwhite is the same resolution as the Oasis (300ppi).
As for storage, 8 GB is plenty for plain books, but if you want to read comics or listen to audiobooks the 32 GB version may be good.
The new Paperwhite, has, compared to my previous Paperwhite 3, a higher resolution screen, double the storage, bluetooth for headphones (for audiobooks, not sure about mixed format such as language learning books), is waterproof, has a flush screen (doesn't trap crumbs), and is fractionally smaller (just enough that an old case is no good). It may be a bit faster, but not enough so to be really obvious, given the 6 month gap.
If you've a working Paperwhite, it's probably not worth upgrading unless it's an original that's starting to show its age, or unless you want audiobooks.
Against other Kindles like the Oasis, it would be a matter of how you view the trade offs between price, screen size, portability, and page buttons rather than anything else.