As title says, End Stone Bricks are much less durable than raw End Stone, and the Ender Dragon can destroy it.
End Bricks appear to have the same blast resistance and hardness as sandstone.

This is inconsistent with other blocks' brick variants:

• Stone <= Stone Bricks (+ its variants)
• Prismarine <= Prismarine Bricks and Dark Prismarine
• Netherrack <= Nether Bricks
• Clay <= Bricks
  ...
• End Stone !<= End Stone Bricks

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How to Prove:

*Ignite TNT in a thick bed of End Stone, and then ignite another TNT block in a thick bed of End Stone Bricks. The bed with End bricks should have a much bigger crater than the End Stone.

*With mobGriefing set to true", have an Ender Dragon fly into End Stone Bricks.