Hi mike,
In your post you indicated an appreciation for peace and quiet....didn't care for the HST whine, liked the quieter Kubota engine. I like it quiet too.
Keep in mind that running the HST you'll be setting the engine speed at a 'high idle' probably over 2000RPM and leaving it there. Progress over the ground will be controlled by the HST pedal. You can, of course, throttle down when the load is light but to simplify things, it's usually kept at high idle. The power is kept online and tapped as needed by the HST; either for speed OR pulling power.
Every diesel I've operated makes a fair amount of racket at 2000RPM .... certainly more than it makes at 1200 or 1500RPM.
Point is, with GST, you can select an appropriate gear and, quite possibly, get the job done at 1200 or 1500RPM; and there'll be MORE jobs you can get done at the lower RPMs as the transmission losses will be less. Speed AND pulling power, in any specific gear, will be proportional to throttle setting. When you need neither, you back off on the throttle and enjoy a moment of quiet /forums/images/graemlins/smile.gif. Using the foot throttle makes this quite natural and the quiet moments more numerous.
Don't know about the others, but I hate the sound of an engine revving when it could be accomplishing the same thing at low RPM...but that may just be me. Besides noise, there are things like fuel consumption and wear that go along with the high RPM. Rarely are my gear tractors operated above 1800 RPM. On the other hand, the HST NH TV140 that I operated for the county last winter rarely operated below 1800RPM.
Now that I've thrown gasoline on this perennial debate, I'm outta here /forums/images/graemlins/grin.gif!
Bob