That's actually 91 RON and 97-ish RON. The figures are displayed in AKI, apparently.
What car do you drive? Is it FAST?
Higher than what your engine is meant for is no benefit, but lower can damage the engine.
It totally is a measure of quality if you would consider that fuel that makes your engine break as bad quality fuel :C
Higher RON can withstand higher pressure (turbo chargered cars, for instance) before auto igniting.
Some clever cars and bikes can adjust engine timing to suit the RON of the fuel, too :O
{{{wikipedia}}}
Rapid summary: RON is a measure of 'explosiveness' and / or octane. Contrary to VERY popular belief, high octane fuel is LESS explosive than low octane fuel. What this does is allow the fuel to be more compressed without spontaneous ignition, meaning when it's deliberately ignited by the spark plug (At JUST the right moment) the energy created is much more.
Essentially, high performance cars have high compression engines. Most cars, well, don't.
Running high octane fuel in a normal car will make zero difference, whatsoever*. Running normal fuel in a high compression engine will do one of the following:
-Cause pre detonation, where the fuel explodes prior to the spark plug lighting. This is pretty bad for the engine and obviously kills performance
-The ECU will detect the above and back the timing off. Engine will be fine but performance suffers heavily
*Regardless of what someone will no doubt say, any differences in performance are either because the car is specced for high octane fuel OR the high octane fuel happens to have better detergents in it which clean the engine.
Conclusion: Unless your car really is high performance / high compression, don't waste your money.
Hey, wait a minute! I drive a Land Rover(at least part time)! It is a 1989 and I wouldn't say that it is a paragon of British fuel economy...
Wish we had Tdi 5s here.