I want to buy a co2 laser cutting machine

I think you are correct.

Two comments I would add to your list

The exhaust system is probably sized more towards the work envelope size rather than the power of the laser itself. But I’m pretty sure you realize this bc you ended it with a ?.

The only other thing that MIGHT be different is the laser head and lens. I ASSUME that they could be identical but I do not know if a lens set up for 40w would suffice for 150w. It’s very possible that the same setup will work for both units but I do not know the technical side of the Lens/Head.

No worries. All opinions are welcome! Keep’em coming!