I have 35 years in fuels manufacturing, production, lab, and additives. But you should still take what I say here as information only, and use your own judgement to do what's best for you.
This information relates to fuels in North America only. The rest of the world operates in a similar fashion, but I have little experience off Island NA.
If you have a high-compression engine, or it's turbo- or super-charged - you need a higher octane fuel to prevent destructive detonation in the combustion cycle. The Versys engine is none of these things.
The Octane Number is an indication of a fuel's resistance to detonation under compression - so-called pre-ignition. Often heard as a 'knock'. The fuel is self-igniting before the spark event, often before the piston has risen to where it provides maximum compression to the mixture, resulting in excessive pressures - ie. the fuel mixture goes BANG! before top dead centre, trying to force the pistion down (and your bike into reverse...) while the rest of the parts of the engine and the motorcycle are still moving 'forward', driving it up. That's it. It does not directly relate to energy content, or even flammability. Flammability is not a term generally used in the industry to describe a fuel's characteristics. It's all 100 % flammable, hopefully. Maybe a more correct term would be 'flame-front propagation and sustain", but that's more technical than we need to be.
Your engine is designed to burn fuels containing ethanol. Ethanol is an excellent octane enhancer, and flame-front stabiliser - and despite containing less actual calories - energy - than gasoline - the increase in combustion efficiency it imparts in a modern engine will offset the small energy deficit of 10% ethanol in your fuel. Don't be afraid of it, just buy fresh fuel from a busy station and don't let it sit in your tank for months at a time.
There is very little difference in the actual energy content between the low and the high octane (so-called "Premium") gasoline. Pure ethyl alcohol has an octane rating in excess of 100, but contains 2/3 the energy of 'pure' gasoline. And since 'pure' gasoline is a blend of many different compounds, there is no such thing as pure gasoline - unless you can find 100% C8 Octane somewhere. I see it in the lab - and nowhere else. It's used as a reference fuel in "Knock Engines -a very accurate engine used to generate that MON - motor octane number for your octane rating. RON - is the research number - the octane number calculated by a spectral and chromatographic analysis of the fuel. Always higher than MON. The real world has limitations...
The myth is that Premium gas is somehow better in some way than regular gas. That there is more or better additives in it. That it has more 'energy' in it. That it somehow 'works' better in some cars. Well, we certainly don't design it that way, but that doesn't stop the Ad Men and Women from marketing it that way... I shake my head every time I see that Shell V-Power Nitrogen Enriched commercial...
Mostly not true. Usually the ONLY difference is that Premium gas is blended to a higher Octane number with slightly different components. It is possible that there is an Octane-enhancing additive added to the fuel to raise it's Octane rating. There are several that work, most are alcohols, in Canada we can use MMT. It's a 'lead substitute' that uses manganese.
There is no difference between buying at a Branded station verus an Independent. It all comes from the same tank. The Refinery does not have separate tanks - "Good" gas for it's own stations, "Cheap" gas for the independents. There *may* be a tiny difference in additive packages - but in no significant way that a consumer would notice or need to be concerned about.
A thing to consider - it's always best to use the freshest gas available. Since Premium is often more expensive, it is often the 'oldest' gas at the station - the least fresh, if you will. Regular outsells Premium in North America 100 to 1.
The big branded companies usually use a bit (and I do mean a bit, an almost immeasureable amount) more of their additive package in their branded fuels so they can legally advertise it as 'different' from a competitor's fuels. But it mostly makes next to no measureable difference in performance of the additives - it's a well-known science, there's not much new under the sun.
For my Versys, I buy Regular gas at a busy station that sells a lot of it, ensuring a relatively 'fresh' supply.
Fuels manufacturers love people who buy Premium, The margins of Premium gas are HUGE! Hey, somebody has to pay my pension.
Hope this helps.