I wouldn't consider these huge issues, but there's 3 areas where I think the miir design suffers relative to the chemex. The pourover part looks like just a single wall. Obviously the chemex is, too, but according to a quick look on wikipedia, stainless has ~10x the thermal conductivity of borosilicate glass, so your brew chamber is going to cool more quickly. No clue if it would be enough to make a difference in brew temp, though.

The stainless carafe part sounds good, too, but stainless travel mugs almost always get lots of coffee residue buildup, and it's a bit of a process to get them properly clean to the point where you don't smell it. I always end up washing with baking soda and/or citric acid a few times. Glass stays cleaner, and it's also easier to see how clean it is.

Lastly, it might just be me, but every once in a while, my scale times out if I'm doing other stuff while making coffee, or I'll make coffee without a scale. It's really nice to be able to see visually how much coffee there is in the carafe.

is your chemex higher capacity? seems like that miir might only hold ~3 cups comfortably, 4 at max.