His or him

[Raymott]

No there is one more post of mine in which someone told me to use "his" because of possesion. I didn't understand your meaning. You said "in preference to", what does it mean?

"In preference to" means "rather than". "Use A in preference to B" means "Use A instead of B".

What you should ideally do, if you want to pursue this, is post the link to the post which said you must say "him" and the link to the post which says you must say "his". Then we'll be able to see them in context, and better diagnose the problem you're having.