He would choose Axis, if it were on offer. Irori's worshippers are tolerable; Abadar's aren't, but at least they're useful. He could probably be happy there, and -- he can't deny that any other choice carries risks.
It's not on offer, so how he feels about it is irrelevant.
The Abyss is right out. All the downsides of Abaddon, and even if he survives he'll, what, have the chance to go around bickering with demons for all eternity? It's a wonder anyone is willing to go there voluntarily.
Menas Karam is not an ignorant man; he knows that most petitioners in Hell suffer. He's sure most of the people he condemned to death would take Abaddon in a heartbeat, if it meant avoiding that. But--
--If he goes to Abaddon, that's it. Everything he's ever achieved is set in stone, and he'll never be anything more than that. In fifty years, people will barely remember him, no matter how perfect a court-assistant he was in life.
If he takes Hell's offer, at least he has a chance. He can advocate for Hell without having to pretend to care about the feelings of pathetic weaklings unable to stomach the idea of spinning evidence the way a judge wants to hear.
Besides, Hell isn't stupid. They wouldn't waste someone as gifted as he is on being a paving stone.