I have a Kobo Mini and 2 Paperwhites. This might not be the most useful comparison but it's what I have. I find the Kobo to be far more customizable but I still do most of my reading on the Paperwhite. I keep short stories on the Kobo and use it for that.
I did install extra fonts on my PW and I did find one I preferred to it's built-in fonts. I don't recall which it was now. This was on one of the Paperwhites, to try it out. I went back and forth between the two Paperwhites for a while and soon decided that, while I did prefer the new font the difference was so small it was hard to really care. I've since removed it because I prefer my devices to be stock.
I've been reading about the new Kobo Aura and wondering if that might be something I'd like even better. I really like the idea of the flush bezel. I may eventually get one to try it out. I haven't decided yet. What holds me back are two things: the Amazon ecosystem is just so good that no-one can compete with it. And that the Paperwhite is so very good that even if I like the Kobo better, who cares!
I realize I'm jaded. The Paperwhite is perfect and I find myself lusting for perfecter. Should I give in to that?
Barry