Is there really that much of a difference in how the saw runs?
From a cold engine, my two-cycles start just a little easier (especially in sub-zero weather) on the 87 octane... but that's where the positives end.
Once the engine warms up, running 87, the idle becomes erratic and I'm constantly fiddling with the adjustments - Running 91 octane I can start a cold saw and set it down at idle, and it would probably run until the tank was empty... and I rarely have to fiddle with the mixture screws.
I definitely notice a difference with acceleration running 91, no hesitation or sluggishness - I can't say that about the 87.
I have to run the saw a bit "richer" on the 87, which increases fuel usage (not a big deal, but noticeable).
The engines just sound "healthier" on the 91 over the 87, I don't know how to better explain that, they just do... there's a "sharper note" to the exhaust.
It's near impossible to hear pre-ignition in a small two-cycle engine, but my old Harley Davidson golf cart has a 250cc two-cycle and I can surely hear it when the engine gets hot running 87... and it will "backfire" (detonation) occasionally on deceleration.
Again, near impossible to tell on small two-cycles, but the golf cart 250cc positively runs cooler on the 91 octane.
Power? Well, maybe I can't actually "feel" it, but the better an engine runs the more power it's likely making... that's just the way it works.
The operator manuals for the Stihl equipment both dad and I have (pre-EPA chainsaws, weed-whips, leaf blowers, etc.) all specify a minimum regular (non-ethanol) grade lead-free octane fuel of 89 (R+M)/2 (US-Canada) or 91 ROZ (Europe, which is approximately the same as 89 US). Honestly, I don't know what the "newer" engines call for, but if it's "lower" than previous engines than they've been "de-tuned"... that's just the way it works. Any 89 octane pump fuel I've ever seen in this state is blended with 10% ethanol, and I won't use it... besides, any small engine (2 or 4 stroke) I've ever run 10% ethanol in has run like crap.
addendum - By-the-way, I haven't used "gasahol" in anything since the very early 80's and I've never needed to replace fuel lines or carburetor diaphragms in any of my small engines... some of them well over 20-years old.