When using Kobo's kepub format, you basically get a modern Webkit renderer. (Note that regular epubs trigger the much worse ADE renderer.) It's a pity you have to use their kepub format, but fortunately kepub is just epub with some extra HTML. I've been hoping for years that Kobo will get its act together and enable their good Webkit renderer for plain epubs so we can stop having to make kepubs, but that hasn't happened yet.
Additionally I believe you can install other software like koreader on Kobos, so if you don't like Kobo's own software you have options, unlike Kindle.