Every engine is optimized for a specific octane number fuel.
So if 91 is good enough, then running with 95 will not give your any benefits.
Running with cheaper 91 in an engine made for 95, will cause engine knocking/pinging, which in the end can damage your engine.
But TS is actually not way off in his thinking.
Generally speaking, an engine with higher compression ratio, requiring higher octane number fuel is actually more efficient, more powerful and will provide a better fuel economy compared to a lower compression ratio engine running on a lower octane number fuel.