Quite an experience on the two rental Harleys with 103ci V2s this past weekend.
Bike #1 was a '13 Dyna Glide something cruiser. No engine vibration to the grips (except when it was at a light - then it would rattle your teeth out), however tons of vibration from the road. You could feel every piece of gravel buried in the blacktop.
Bike #2, the Road King tourer was another story. No vibration to the grips at all -- road or engine. This bike had rubber engine mounts but the difference wasn't noticeable by me. I did about 7 hours on this bike on Sunday and my throttle hand never got numb. A little sore but no tingling sensations at all.
The bikes rev up to about 5400, with most riding done at about 3K. I'm sure that has a lot to do with the vibration issue. The RK was about 800 pounds so that may have been a factor as well.
Another factor could be the diameter of the grips. They were somewhere in the 1.25 to 1.5-inch range - much bigger than my F800ST's.
Mike