GPT 5.6 sol or Opus 4.8/Fable for android kotlin

I am planning to subscribe Max Plan to either codex or Claude
for android kotlin development.
Wondering if people can provide their genuine feedback on which model they prefer for Android Kotlin development and some concrete example of issues/good parts.

For my part, prefer GPT for technical parts, but Opus/Fable seems better at Design level.

Thanks.