I was told the exact same info directly from the dealer when I bought my '16 last July. They said I could use either app, but it would probably be in my bast interest to use the My Chevrolet app as it was the only one that was going to be supported going forward. No reason not to believe them.
EDIT: I just checked the Apple app store.....the My Chevrolet app was updated about 3 weeks ago, the OnStar app was updated 15 MONTHS ago. Thats enough proof for me
EDIT: I just checked the Apple app store.....the My Chevrolet app was updated about 3 weeks ago, the OnStar app was updated 15 MONTHS ago. Thats enough proof for me