Hi
I think The question at issue is Windows-application or Web application(WPF for win-app VS asp for web-app), Which one is better for you and your project?. In this case your platform is network and your program must work on the net. so for this usage Web-app is better but there are a lot points existing which can make decisions hard. Network platform has great challenge.(according to my personal experience)
Working with web-app by asp.net is nearly hard. you must try to handle many thing's for web-app(request time, session management, even poor UI in comparison to WPF, j-query, etc ). Remember this is not as easy as simple web site.
But win-app is good for network with this condition: "local network"(mpls is almost the same). Absolutely developing win-app is easier than web-app ("At least number of users expert in net-program developing"). for this case WPF has many good things(UI , command, etc) also has many challenging point(like multi-threading and lack of expert developer in this field ) . I'm rather with wpf than asp but decisions is yours
And chalk point to good thing Silverlight but if you want to use this you must look at prism framework : http://compositewpf.codeplex.com/
I have recently developed a project separately with asp and silverlight(prism framework). developing silver-light version is too hard and takes more time than asp.net version but at the end SL-ver have great look nothing else!
Burns pointed to good issues about wpf. also consider Artemiy's post. your environment conditions is same for both of them. WPF/ASP can work with scanner and soft-phone cuz the base of both is on C# and .net library
Finally what ever your decisions is you must hire advance developer at least develop one business-app for the network platform.
