HTC One M9 vs HTC One M8: What's the difference?

Image may be NSFW.
Clik here to view.

HTC announced a new flagship handset, the HTC One M9, at Mobile World Congress 2015. We've now fully reviewed that phone, the replacement for last year's popular One M8. At first glance it looks to be very similar to the M8. So is this more of the same,...