BILL S. - IMHO, engine vibration is all relative to the size of the engine and it's components. Even the little 7 & 8 HP engines vibrate. A 16 HP will vibrate a certain amount, and a 14 hp will vibrate about 7/8ths as much, etc, etc.
There are things that can reduce the amount of vibration. The counter-balance gears Kohler used on 12, 14, & 16 HP engines were short lived, quickly designed and not robust enough for their job. I refer to them a grenade gears, as in "Hand Grenade"
Look at the colorful boxes at the top of this page, on the left, Kirk Enginess, click on the box and scroll down the page and read up on Dave Kirk's balance weights he makes for Kohler engines. I had Dave balance a K321, 14 HP engine several years ago... it runs smoother than the K241 10HP engine it replaced. IMO, They're the best was to modify a Kohler to run smoother and longer.
I bet if you polled the members here, just about ALL of them would take a 1X8 or 1X9 model tractor. I had a 129 for 15 yrs, was almost a basket case when I bought it, repainted it, refurbished it, rebuilt the engine, was a reliable efficient tractor for many years after all the work and expense.