As Lougle says, nobody here can give an opinion on the appeal panel's decision, because we haven't seen the evidence from you or the school and we haven't seen the precise wording of the decision letter.
However, on the basis of the snippets you have posted here, I think there are some points you could raise in your complaint, as what you have posted suggests that the panel might (I emphasise might) have taken the wrong approach and might have misdirected itself.
Firstly, on the finding that "I am not convinced that XXX is the only school that can meet his educational and social needs": This (in my view) is going too far. The panel should be considering whether the preferred school can meet the child's needs better than the allocated school and can offer something which the allocated school cannot.
Para 3.8 of the appeals code 2025 says:
"3.8 The panel must balance the prejudice to the school against the appellant’s case for the child to be admitted to the school. It must take into account the appellant’s reasons for expressing a preference for the school, including what that school can offer the child that the allocated or other schools cannot. If the panel considers that the appellant’s case outweighs the prejudice to the school, it must uphold the appeal."
It does mention "other schools" but it doesn't say that the panel has to be satisfied that the preferred school is the only one capable of meeting the child's needs.
Our authority takes the view that appeal panels should not stray into arguments about whether a third/fourth/fifth school could also meet the child's needs, because the appeal is not for any of those schools and taking those schools into consideration and expecting the parent to prove that only the appeal school is suitable would be raising the bar too high. That seems right to me.
Secondly, on the finding that "Ideally this is supposed the medical and social criteria where they already rejected saying the same": This seems to imply that the appeal panel took the view that, because the medical-social need panel did not give admission priority to the child, the appeal panel has to reject the appeal. As I said earlier, the two panels have different purposes and make their decisions against different criteria. The appeal panel is looking at the bigger picture of the prejudice (detriment) to the child if not given a place, and the prejudice to the school in having to accept an additional pupil, so is free to reach a different decision where the evidence supports it.
So, if you are taking this further, you might want to highlight these two points and any others.