Carrier suitability mattered more than headline aircraft speed

Would the Hawker Henley or Hotspur have made a better carrier dive bomber than the Blackburn Skua?

Not automatically. Their higher speed did not include the Skua's carrier-specific design, while a better engine could have improved the naval aircraft itself.

The quoted speeds of the Hawker Henley and Hotspur do not establish that either would have been a better carrier dive bomber than the Blackburn Skua. Neither Hawker aircraft is recalled as meeting carrier specifications when it achieved those figures. The Skua's slower performance has to be assessed alongside those naval requirements. A better engine could conceivably have improved its speed and changed its poor reputation.