Let's address the obvious here first. There are two devices here. There's speculation going around that HTC has multiple variants in the works, a basic version and a "plus" model that comes with a fingerprint reader (which looks like a button). We don't have confirmation of our own, but Blass's track record comes with some weight.
If these latest renders are true, they show the M9 benefiting from some of the hardware HTC has introduced in the past year. The BoomSound speakers have gone from full-size grills to tiny slits, like the ones we've seen on the Nexus 9. The front-facing camera is centered, as it is on the Desire Eye (which happens to have an impressive 13 megapixels).
The reduced grills leave room for the model on the left to have a lower logo, removing the black bar underneath the screen that seemed like wasted space following the M8's removal of the M7's capacitive keys. The one on the right still has the black bar, and when combined with the fingerprint reader, looks pretty cramped. Its spacing also seems a bit off next to the model on the left. If these renders are legit, hopefully the phone on the right remains a work in progress.