I picked my newest ereader to be a kobo for multiple reasons - but the biggest ones were price and software.
Price - I got a H2O for USD$200 (they're more expensive overseas than in the US) - to get a kindle with physical buttons I'd have to pay out the nose for an Oasis which runs at around USD $305 without ads.
Software - I like 2 things a lot about the kobo, that convinced me to switch.
- It shows the cover of the book you're reading when it sleeps, which is just cute. I think kindle does this now, but not sure.
- PAGE NUMBER. PAGE. NUMBERS. This was the biggest feature for me. I love it so much. Being able to see how many pages I have in a chapter lets me judge if I can plow through another chapter through bed, or before my lunch break ends... etc. It blows my mind that Kindle doesn't have this feature.
There are other minor reasons, like wanting to just switch away from Amazon when I can. But the above are the main two.
Kobo isn't perfect (mostly I have issues with the foreign language dictionaries *cough Japanese*). But it's way better than kindle, at least for me.