I only use the groundglass on the speed graphics. I tend to use odd lenses which wouldn't be easy to make work with the rangefinder. I also feel good about verifying my image is in focus on the ground glass.
I really like the focal plane shutter. It's my primary reason for using a speed graphic. You don't get with the super. I like the older ones that went from 1/10 to 1/1000 better than the newer ones that only go from 1/30 to 1/1000. But the newer speeds have the graflock back and the 4-sided metal hood, and the better adjustable front standard which are nice. Might need a frankengraphic before I'm done.