Google has done a great job getting their keyboard to what it is today. It started off as the default keyboard that many people seemed to ignore and instantly switch out for another 3rd party version. This past year Google has really stepped up their game, and is quickly coming one of the top contenders.
Google has decided to give us a little color back in our lives, by once again giving us a ICS / JB blue option.
The white keyboard was really nice for us on 4.4.x Kitkat, sporting the latest and greatest OS available. However, not everyone is in the same boat, and having a white keyboard might clash with your system look.
Google Keyboard is the most responsive keyboard with great prediction and auto-correction for my terrible English skills. It has quickly become my keyboard of choice, something I was not able to say a year ago.