In one of my previous jobs I was responsible for helping to develop a native Windows client. At the same time, a web client was developed by another team. Although the native client had some advantages (it was much quicker and generally more reliable*), the web client was much more successful. I suspect this was mostly down to the deployment issues you have with a native Windows client. Even now in a world of ClickOnce deployment, web clients are still preferred by a lot of customers.
* This was no reflection of the development team working on the web client. It's just that, all other things being equal, writing a native Windows client is much simpler than writing a web client.