1. Even pretty cheap desktops can be packed loads of memory, and can run a lot of virtual machines.

2. You can easily swap out/upgrade components.

3. If you are running the system nearly 24 hours a day, a desktop might cope much better than a mid range lap top (regarding life of the components). So use the laptop only while you are traveling or for a demo. When you are home, use the cheap but powerful desktop with loads of memory and easily replaceable components.

Cons are that Desktops consumes a lot more power and generate a lot of heat. and that might be good or bad depending on your climate.