There's nothing really mind-blowing about the benefits of the EPUB3 renderer in Bookari. It's a combination of things, actually.
For one thing, the EPUB3 renderer has more finely graduated font sizes--unlike the EPUB2 renderer where I invariably get to the point where one size is way too small and the next step is way too big, and there's no in between.
Another reason I've switched to primarily EPUB3 is the subject of this very thread. Converting my purchased EPUB3s (and I'm getting more and more EPUB3s when I buy books) is a pain in the butt, and takes time that could be better used reading. So is maintaining two themes (one for reading EPUB2s and one for EPUB3s). Never mind that sometimes I just want to download the ADE-encrypted EPUB3 books and read them immediately without tweaking them. Bookari allows me to do this.
Long story short: I want to read (and archive) one or the other standard (so I don't have to keep multiple setups and switch between them to read my books). And converting EPUB2s to EPUB3 is vastly easier (and quicker) than the other way round.
Only one standard being archived in my library + one theme/app to read them all with + finer font-size granularity + more time spent reading as opposed to converting/tweaking = EPUB3 for me. Making sure everything is EPUB3 is easier and takes less time than making sure everything is EPUB2 ever did. I wised up.
