Mileage would not be consideration since all three have what ST riders consider low mileage.
Accessories could be a flag in my opinion, since alot of folks would rather spend money bolting on gadgets than doing maintenance (think harley davidson owner).
Everyone has their own idea of what is perfect. Some think a bike is not finished until there is nothing left to add on, while others feel it is not finished until all the non-needed stuff is removed etc.
I would decide on which bike by inspection, and inspection alone.
I would inspect the brake system (secondary master cylinder) conditions of pads & calipers, the coolant system (water pump) coolant leaks, oil leaks, fork seals, preload adjuster, any damage hidden under the tip over covers etc.
Pull a plug, check the oil, air filter etc.
Have recalls been done if needed?
Anyone can decide to bail on a bike that runs poorly or too hot, then dress them up with new parts and pass as "never ridden much" etc.
I would pass on a bike with three owners in a short period of time.
Also check the service records if from a dealership (owners could make up stuff).
Does it have a clear title? Hidden DMV costs? Late registration fees? Is it in the person's name selling it? Non-op?
I would only consider a bike that I could inspect, test ride, and has ALL paperwork and current tags, insurance, etc. in the sellers name.
I have seen too many folks limp or trailer bikes to me that they just purchased, and were told by the person selling them, they could hear it run, but due to insurance reasons could not ride it or remove anything to inspect it.
Needless to say, bent frames, forks, steering head stems, coolant leaks, failing water pumps, damaged splines, electrical issues from added on stuff, or the old "I'm selling it for the widow after her husband died" BS.
Or I lost the title during a flood, it comes with a bill of sale only...and I don't have ID or drivers license