The Kindle became big because it is the cheapest ereader on the market. That's because the hardware is deeply subsidised by Amazon.

I don't buy books I loan them from my local library and put them on the Kindle.

I'm not really bothered by why it became big. I'm just saying the Kobo is better, in my opinion, and that's probably because it's not the market leader, so has to offer more.

Quite often the second place competitor has the better product.

The color version takes a lot more light. You'll need the back light on any time it's not in direct sunlight. The color is also pretty muted.

All in all, it's worth buying if you need an ereader and want to use the color features, but I wouldn't recommend buying it if you already have the black and white version.