As a Kali warrior You have my full agreement on Your statement. Only medium and lower speed allows You to control the units most effectively.
The game should be decided by the best strategy and not by who clicks fastest.
However, to become a true all round player and master of C&C I think it is necessary to be able to play every map with GDI and NOD on every map with every possible settings (including every possible speed settings).... then You can say You handle everything C&C can throw at You.
And yes....I mean also being GDI in a bases off 2 units game (it is possible to win) !