IIRC, the GT force wheel was teh official wheel of Gran Turismo 3. It then kind of evolved or simply became the Driving Force. As far as I can tell, they are the same wheel internals. I haven't seen both side by side, but I'm betting button placement is the same also.
Logitech's new wheel, the Driving Force PRO is the offical wheel of Gran Turismo 4, and is a 900 degree wheel.