These are EXACTLY the same pictures taken with both apps on the 930.
Lumia Camera:
https://onedrive.live.com/redir?res...authkey=!AIrHIInUqfM_9E4&v=3&ithint=photo,jpg
Microsoft Camera:
https://onedrive.live.com/redir?res...authkey=!AEHVs3fZFWpGG_k&v=3&ithint=photo,jpg
On the final quality (Lumia Camera WM10 vs 8.1) I can not say anything yet. I'm undecided. I do however tend to agree with you on the app side of things. I still don't really think that the change of OS can have an impact on image quality. The drivers are the same. The software (Lumia Camera) is the same.
I have HOWEVER found out two things:
1. The file sizes are slightly smaller on the Microsoft camera. 1.9MB vs 1.7MB (Again: these are oversampled versions)
2. In the photos app on phone (WM10) one can pinch to zoom further into the picture on the Microsoft camera
The fact that one can zoom in further WHILE the actual file size is smaller makes it obvious to me that the products of the Microsoft camera WILL be inferior. If this makes a HUGE difference in daily usage let's say when using a Lumia 640 I would seriously doubt. In my opinion you wouldn't even notice it. On something like a Lumia 930/950 I think you WOULD notice it (If you would really look for it).
In conclusion: There is a SLIGHT decrease in quality if you compare the two apps. BUT this is also pre-release software. There will definitely be future updates to the software but WHY didn't they just rebrand Lumia Camera? Instead they created a new application which, by my assumptions, is slightly inferior.