You use whichever tool suits you best. We can't answer this for you as we don't have access to your requirements. Here are some things that you might want to consider.
- Do you want to support changing the overall look and feel of your application so that it no longer looks like a standard windows forms application? If so, you should look at WPF.
- Do you have experience building applications using a declarative language? If you don't, WPF has a steep learning curve.
- Will people only be using Windows to access your system? If no, then it should be browser based.
- Do you require complex animations in your application? WPF is better suited to this than WinForms
- Will this be running on Windows XP? If yes, go with WinForms as you will be limited to an older WPF version that is missing a lot of the performance improvements introduced later on