What is the difference between the Console Client and the GUI Client?
From FaHWiki
The CPU console client, also known as the Command Line Interface (CLI) client, or the "no nonsense text only console" is distributed as software only and is not packaged as a "Windows Installer." It is a window into which you can type your answers to the questions.
GUI stands for Graphical User Interface. The GUI Client is a F@h client which is easier to setup and manage by means of buttons, drop-down menus, etc. For example, the whole Windows desktop is a GUI; your internet browser is a GUI.
Note: Both clients use the same FahCores to process work units, so the CPU CLI client and the CPU GUI client fold at the same speed when the GUI is minimized. The GPU client window is open, it may use some CPU cycles slowing performance slightly.
See also: Clients Overview

