Two things:

The customization of text including sideloaded fonts, plenty of margin, line spacing, and font size settings, etc. I've made a habit in the past of always deDRMing my books then converting them with added CSS so I can better read them on an eInk eReader. My eyes are not as young or capable as they once were. I really don't have to go to that trouble with the KT.

and

Kobo actually listens to customer requests and tries to implement them. That is rare in the eReader business. The KT needs a lot of polishing, but they seem to be willing to make it better and in a timely fashion.