There's more to it than a general panther vs medium slug match.
It's a matter of unit preservation. It's easier to retreat out of a bad situation if the enemy isn't faster than you. (or have laser accurate guns)
the simple vehicle smoke is one of the best ability in the game for this reason.
medium tank should be able to outrun what it can't outfight.
and lastly 6.4 2.3 isn't slow. The current sherman tank is only 6.4 2.2 and the e8 even slower at 6.1 2.1.
I still don't understand the point of the thread. Mediums shouldn't be strolling the map faster than anything else unsupported and carefree inflicting bleed as they wish. Panthers won't dive you if you're supporting your armor with AT and snares.