If you are wanting versatility, definately get the welder/generator. It is probably not as quiet as the Onan with the Kubota becuase the Onan generator with the 19 horse Kubota I looked at had two mufflers and an intake silencer, as well as sound deadening side covers. However, the Kubota powered welding machine is WAY quieter than the gassers. It has the D722 engine, which is the same as in my TG1860 mower. So far, I LOVE it. Even if it is a little louder than the Onan, it has the same 10 kw output (as the machine I looked at) and adds the welder, which would be VERY useful around a farm. It has a 50 amp 250 volt 4-conductor plug. The plugs vary to keep people from plugging in too small of a conductor and burning something up. Electrical supply stores have them. You will also need #2AWG wire from the plug to the power box.
Hope this helps!
John