Comparing two oxidizing agents using electron configuration


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> Which oxidizing agent from the pair $\ce{K\_2IrCl\_6/K\_2PtCl\_6}$ is stronger? Explain your answer using their electron configurations. 
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We write the electron configurations for $\ce{Ir/Ir^{4+}}$ and $\ce{Pt/Pt^{+4}}$:


$$\begin{align}
\ce{Ir:\ [Xe] 4f^{14}\ 5d^{7}\ 6s^2 \ &\implies \ Ir^{4+}:\ [Xe] 4f^{14}\ 5d^{5}}\\
\\
\ce{Pt:\ [Xe] 4f^{14}\ 5d^{8}\ 6s^2 \ &\implies \ Pt^{4+}:\ [Xe] 4f^{14}\ 5d^{6}}
\end{align}$$


From those, we notice that $\ce{Ir^{4+}}$ has all 5d orbitals half-filled, whereas $\ce{Pt^{4+}}$ has 4 half-filled 5d orbitals and one filled entirely (which is a less stable configuration);
so it's much easier for $\ce{Pt^{4+}}$ to get reduced than it is for $\ce{Ir^{4+}}$.


Therefore, the strongest oxidizing agent is $\ce{K\_2PtCl\_6}$. What's wrong with my solution?


