I've noticed a connection between the powers of Master Xehanort's Keyblade and the Dark Keyblade that Ansem SoD gave Riku in KH1..Mainly, they can "unlock heart's potential", as seen when Riku stabs Maleficent and MX creates Vanitas by stabbing Ven with his Keyblade. They both can release hearts as well, as seen when MX possesses Terra and when Sora uses the Dark Keyblade on himself. The only power MX's Keyblade is shown to have that the Dark Keyblade does not is when Terra "locks" his heart, sealing away his and MX's memories.