A Desktop PC is usually better value for money and more reliable than a laptop. It will generally be easier to set up a comfortable workstation because the keyboard, mouse and screen arrangement is easier to set up to suit different people.
But there is a BIG BUT! The Desktop PC is less useful if you need to work from other locations. If you only need to work from home rather than the office and you already have a suitable PC set up at home, you can manage that with a Desktop PC in the office. You can leave the Desktop PC in the office running and then use a package that allows you to control it from home.
Laptops provide much greater flexibility, but they are more expensive. If you plan to work long hours in the office you also need to invest in monitors, wireless keyboards and mice as well as docking stations to be sure you can set up a comfortable workspace.
In each case it is important to understand what you intend to run on the laptops or Desktop PCs so that you can get help in buying something that will support you for at least 3 years without any issues. The fact that you plan to use them for business in a network context also means you should avoid buying anything running operating systems intended for Home Users. These will not play well on your network.