All Politics Aside (Score 1)

The decision depends on the background of your developers. With either language you can develop a highly reliable world-class application (folks do it every day). If your developers have experience in developing Pascal, C, or C++ applications then Java is a better platform choice. If your developers have backgrounds in RAD development languages such as Visual Basic, PowerBuilder, etc then .NET would likely be a better choice. The project ramp-up expenses (training-prototyping-design) will likely be very large, but you can minimize that by bringing in a consultant (or two) that is an expert (not just familar) in the platform technology that your group decides upon. Do not fear losing face by letting them lead because if you hire the best available in your market their resource value will be priceless.