The updated MS Health app lists 4 items, but it's unclear if they are exclusive to Band 2.
- UV Monitoring*
- Logs stairs*
- Wake up refreshed without sleeping in*
- Create customized workout on web dashboard.
* Has a link to "Learn more about Band 2"
For UV, the web app says: "UV exposure reminders are available on Microsoft Band 2 when the UV tile is pinned". While I know the Band 1 can take spot measurements, it appears Band 2 will monitor your exposure.
Logging stairs is no doubt Band 2 only - it has the barometer.
If optimal wake-up is available on Band 1, I'm not seeing where to set it. So that might be another Band 2 only feature.
It looks like there's no limitation on creating custom workout using the web app. (It's also the only "new" thing that doesn't link to Band 2)
Nothing indicates that VO2 is exclusive to Band 2 - I think the claim is that it's exclusive to MS Band. However, I did notice this from the web display: "The Microsoft Health app estimates your VO2 max by analyzing the relationship between your heart rate and speed during activities tracked in tiles like the Run Tile or the Bike Tile." So it sounds like you may have to go for a run or bike - perhaps with GPS on so it can estimate your "output". Now I understand why it hasn't come up with a estimate for me - I've always used the exercise tile in the gym. It only knows my heartrate.
In addition to a display that's about 20% taller, I'm suspecting that the hardware may be beefed up. That would explain why some features are not available on 1. So the disparity between 1 and 2 may grow with time.