Print your QR code to a static link that you can then control where it redirects to.
QR Code -> [www.Your-Webpage.com/redirecttoapp.html] -> [Your webpage redirects to app store]
You can then change it at a later date to point to anything you want without having to reprint your cards should the need arise.
Edit:
Here is the URL Schema for the Apple AppStore.
Just A thought but you could also build in some Browser Detection into your Redirect page.
E.G: If iphone redirect to apple AppStore, If Android Redirect to Market Place.
If you don't have a android app you could redirect to your business webpage.