I think the line of thought is that a jury is not as easily bought, harder to threaten, and better at ironing out the moral ambiguities that can be the failings

I think the line of thought is that a jury is not as easily bought, harder to threaten, and better at ironing out the moral ambiguities that can be the failings of a single person. However, a judge and no jury is certainly more expedient, neither is infallible in terms of their judgement. That is the reason for appeals.