I have Kindles, Kobos and Nooks. I have a fairly strong preference for the Kindles, partly because their devices have better firmware, in my opinion, but also because the store is so much better.
That said, the Kobos are also good. I've never used their store but I have browsed it a bit and it looks fine. Their firmware is a bit buggy but only a little bit and mostly with respect to side-loaded books.
If I could only have one reader it would be a Kindle. If I could only have a Kobo that would be okay too. I'm glad I'm not stuck with just one reader.
Barry