Yes, I think using ASP.NET would be a wise choice. You don't mention your experience so I can't factor that in. If you are an experienced ASP programmer then you may want to go with what is easy for you because there will be a learning curve you must factor in. But considering that the final release of .NET will come some time around the first of the year, if you start with the beta now, from what I've been told, the port to the final version should be relatively easy and shouldn't delay your project. The pluses for ASP.NET are a much more powerful development and debugging environment (I wouldn't consider ASP.NET without also using Visual Studio.NET as the development environment) and compiled executable code translating to better performance of your web site application. Neither choice is bad but if it were me I would be recommending ASP.NET.
Kyle
Here's what DavesTips had to say about Visual Studio.NET in the C# forum:
I'd say, once you've used the fantastic VS.Net IDE, discovered the incredible ease of writing say a web database application full of complex controls with just a few mouseclicks, walked through the code running on a web server with the amazing debugger and successfully got something up and running without spending ages wondering why activex objects weren't being instantiated and so on, and finally rolled out the app with a simple copy, you'll be wondering why you felt so fond of that old-fashioned way of doing things that you were struggling with for so long...and then you'll notice that those who started learning with the .Net Beta have a long headstart on you for all those contracts that will be coming...
