Some points to be made for ASP.NET:
The pool of ASP.NET developers is much larger then the pool of WPF developers.
Which means you can probably find qualified ASP.NET developers easier.
ASP.NET is probably more future proof, chances of WPF getting large changes and being hard to port to later versions is probably larger.
Also keep in mind that the focus of MS seems to be on Silverlight so there might be a consolidation down the road which makes WPF obsolete.
More mature eco system of ASP.NET makes for more out of the box solutions to use to solve problems.
With multiple locations you might be able to skip a few layers and go directly to a website?
