Your point about the software ecosystem is very good. I think the advantage you're talking about stems mostly from how Hololens is a first-class Windows 10/10X

Your point about the software ecosystem is very good. I think the advantage you're talking about stems mostly from how Hololens is a first-class Windows 10/10X platform now, serving as one of their flagship new platforms for their new OS. It was clear from early on they wanted Windows Holographic to be clear extension/continuation of their goal for UWP to be the new write-once, run-everywhere platform (even if that goal was a bit aspirational/unrealistic). That positioned Hololens as a more competent general-purpose computing platform. That's a valuable perspective to have on what AR/XR is supposed to look like: new, but not entirely new, and flexible enough to be able to run the old software.