Found this in the VS1400 Service Manual:
FUEL AND OIL RECOMMENDATIONS FUEL
Use only unleaded or low-lead type gasoline of at
least 85 - 95 pump octane (R+M2-method) or 89
octane or higher rated by the Research method.
Like Skrapiron said "Use anything at the pump except E85 and diesel."
I think your best bet is to buy the bike and keep records. Try the different fuels and see which one best meets your performance expectations as to mileage and performance.
The bike is like a cheap date, she don't care where you take her to eat only that you take her out.
I find normally that my C50 runs fine on any gas. It gets a little better mileage on "real gas" however I don't sweat it, unless running on the slab for extended periods and imagined or not I feel less vibration when running real gas and sometimes adding high test.
ride an 05 c90...have put almost 50k miles on it since I bought it and have run all types of gas and ended up using the regular...sure some will give you reasons to use a higher grade octane but I really couldn't tell any difference...definitely hasn't hurt the bike any.
The level of ethanol may affect bike performance so that may make a difference in your area. I believe the manual says regular gas (87 octane) and that's what I use and it works just fine, with no significant difference when using higher octane gasolines.