I don't think being a commercial app necessarily rules out .NET over Win32 platform. It's reasonable now to require XP or better. Most will already have .NET installed, and if not, then the installer could install it.
the .NET app would have a smaller footprint. Unlike Java apps, the UI speed of .NET app is indistinguishable from a Win32 app. It would probably take less hours to develop, and since the goal of a commercial app is to make a profit, that needs to be considered too.
Win32 apps must be installed and uninstalled. .NET click-once remove this burden, allowing just the server image to be updated, and all the clients get a fresh "install" the next time they run.