Well, last week I lended my Sony to someone who's eager to try an ereader before buying one and I was showing the Mini and the Aura to my brothers. Both of them asked my was choice went to Kobo.
Thinking back, I knew the firmware wasn't optimal, but I put more value in good hardware knowing that the software part can be managed later (since I am far from gifted in this industry, it meant expecting people to come up with hacks and plugins).
Don't forget that I'm a Linux user so I'm used to frequent updates; some fixing things, some creating other issues 
The second important reason was to have a device which was the same (hardware, software) in other coutries (the Sony isn't). So I could display the menu in Japanese and have the Japanese dictionary as well as other dictionaries.
My needs were clear and I don't regret the Mini nor the Aura. The hardware is what I was expecting it to be and I have all the languages that matter to me
If my needs were different or if I had used another brand before*, surely I would sdee things differently.
*my 650 can't have PRS+, so it's nice but with a lot of limitations. Once again, proof that a community can turn a good device in a best of its category one.