For people on Kobo: Koreader handles standard epub way better than the native reader.
If you've ever tried reading an epub using Kobo that you didn't buy from the Kobo store, you may have noticed that highlighting text is very laggy. Koreader has no such lag.
This can also be fixed by converting books to KEPUB with Calibre, it'll also (for some reason) make page turns faster.
I find it easier to do this using kepubify in a script
I believe Calibre (very) recently added a feature to make conversion to kepub automatic when transferring to a Kobo, so things may have changed on the ease of use front.
Yes, that's true, but I'd rather keep them as ePub so it will work well with other readers.