I've always used the digital speedometer.  Have since I started, and now it's habit.  I'd rather use the analog, but out of habit as I said, I've stuck with the digital gauge.
Now that I'm forced to use analog, I'm happy.  I'd rather use it, and I have to now.
As for the GTR cars having a display like the FBM?  I certainly hope not.  I hate the look of a gauge display hanging in mid-air not attached to anything like in the open wheelers.  It is so distracting, and one of many reasons of why I don't drive the open wheelers much.
Put the racecar gauges solidly mounted on or in the dash, and I'm fine with it.  Hanging in mid-air like it is now, since I have a wheel mounted to the desk in front of me already, and it looks ridiculous and distractiing.