You forget, a mere 0.8 Mhz increase represents an 11% increase in performance on these old machines!
The modern equivalent is to compare a Pentium III 650 to a Pentium III 733, again approx. 11% increase in performance.
Or a Thunderbird to a Duron at the same clock speed, ~10% performance increase.
Do you notice the increase in FPS between these CPUs in your favourite games - of course you do (if the vid card is not limiting the performance).
3d (vector) games did run faster on the ST - I've owned both machines for comparison.
After all why would I lie, I've already said the Amiga was by far the best and my preferred machine for like 95% of games due to it's awesome sound and custom chip graphics capabilities.