Hey Justin, hey Van Jones @WhitePineWorkshop,
I would strongly avoid a 110 V spindle, for the reasons mentioned here and here.
Also if you use a 65 mm spindle on the Original Series with their Z-16 assembly, you got to know that the spindle does not clear the stepper and brings the “spindle back bumps the stepper cage problem” with its chatter problems.
Regarding the 1.5 kW or 2.2 kW spindle choice, I would always choose the 2.2 kW model because you can always use less power and usually it’s not a big price difference. The 80 mm models are available with ER-20 collets which means tools shanks up to 13 mm. A ER-20 spindle has a larger axle diameter than a ER-16 and is somewhat stiffier, since larger bearings are installed. Larger bearings means longer life and less heat. A larger shaft diameter means more stiffness and more resistance against vibrations (chatter).
If you considered 65 mm spindles, yes there were problems with hairline cracks on water-cooled models and on the Onefinity Standard Series, they don’t clear the stepper cage and bump it with their back if not slid much downwards inside the clamp, which augments the danger of chatter, while with the optional 80 mm spindle mount, all spindles clear the stepper. On Elite Series, both 65 mm and 80 mm spindles are said to clear the stepper cage.
These questions are thoroughly answered in this forum. We have a search function here.