HTC One M9 vs HTC One M8 screen-to-body ratio comparison: which one's more efficient?
The One M9 has a slightly smaller area, which lets the display occupy more of it.
Thankfully, not only is the HTC One M9 not any worse than its predecessor, it's actually a little better! The HTC One M8, which has a 5-inch by diagonal display, has a 66.71% screen-to-body ratio. In comparison, the HTC One M9, which too has a 5-inch display, has a 68.52% screen to body ratio. We owe the difference to the subtle reduction in the device's dimensions. They are 5.76 x 2.78 (146.36 x 70.6mm) for the HTC One M8, and 5.69 x 2.74 (144.6 x 69.7) for the One M9, respectively. As you can see, the latter has a slightly smaller area, which lets the display occupy a little more of it.
Of course, one could argue that the black strip with an HTC logo below the display shouldn't really be there in the One M9. But we had the same argument last year with the One M8, and HTC's version of the truth remains the same - it's not wasted space, because it has important hardware underneath. We'll have to live with that, it seems.