Is 'I'm in favour of' considered more formal than 'I'm for', or are they interchangeable? I want to say something like, 'Sometimes people abandon their logic /in favour of/ false hope', but can't help but feel that using 'for' would make the sentence more succinct.
Sometimes, people abandon their logic for false hope'
on behalf of; in favor of; because; since
As you see from the definition they are usually interchangeable. And I agree with simplifying the sentence as you propose.