Sorry .. I voted to close, as this is pretty clearly not a sysadmin issue. But I will give you some help before the vote count gets to 5!
Having been a small company IT Manager, I can feel your pain. There is a lot of FUD around ERP. There are lots of consultants out there offering to help for exorbitant rates (including me!).
ERP is not about technology, it is about business processes. The fact that an ERP looks dated, or doesn't use AJAX, or might (gasp!) be text-based is not relevant. What is relevant is how well an ERP supports the processes that give your company competitive advantage.
Forget the demos. Start with process. Go to each department, and ask them to identify the critical processes, how they are done now, and what about the process makes it critical or gives the company competitive advantage. For instance, the inventory/procurement group might place component orders every day, and their process allows them to know exactly how much to order each day. Then go to the ERP vendors and ask them how they will support doing that process in a way which keeps the advantage or superiority. Have the vendors craft a specific demo of your critical processes.
Some ERP elements are interchangeable. For instance, there are many ways to manage Accounts Payable, and it likely will not matter to your company which one is used as long as the bills are paid. On the other hand, the processes around managing customer orders and inventory might be critical, if the company gets advantage by shipping on time, every time. In that case, you would want to make sure the ERP can support the things that make your order process work.
Finally .. make sure that the operational departments are involved in the process. Over communicate with all involved. If you can't get help and compliance, recommend that the project be cancelled. A new ERP cannot simply be imposed by IT.