The convoy mission tests the design comparison against an operational constraint. The damaged British ships can still escape because they are sailing to Canada and have not yet joined the vessels they must protect. If the convoy were already present, the escort could not simply outrun both the Americans and its own charge. An operational objective can therefore cancel a tactical strength that looks decisive in a ship-for-ship comparison.
Notable Point · 22:01-23:06
Convoy duty can cancel a fast escort's escape option
The British speed advantage only exists because the clash occurs before the squadron takes charge of the convoy; once tied to protected shipping, disengagement would be far harder.