-아/어/여(요)? sounds more direct only when compared to '-나요?' and '-(은/는/ㄴ)가요?'. Personally I avoid using '-나요?' in positive questions - I'm talking about it in speech, not in writing. A₁: 어디 가요? Where are you going? (fine) A₂: 어디 가나요? The second is more informal, a bit cheeky if you ask my opinion. Someone older than me could say something like A₂, but I don't think I could say like that to someone older than me. A₁: 이거 어렵지 않아요? Isn't this difficult? (fine) A₂: 이거 어렵지 않나요? (more indirect, fine) -(은/는/ㄴ)가요? sounds old-fashioned when used with a verb stem, I've heard middle-aged people use it. A₁: 어디 가는가요? Where do you go? / Where are you going? (old-fashioned) A₂: 이게 더 좋은가요? Is this better? (fine) -(은/는/ㄴ) 건가요? is much more common, but its meaning is slightly different. A₁: 이게 더 좋은 건가요? Is this the better one? A₂: 이게 더 좋은가요? Is this better? You were right after all.

Seems to me that endings in -나요? / -(으)ㄴ 가(요)? can be used for self-directed questions, like "mmmm, I wonder...". In that way they are less "direct", but if u add '요' at the end, it is clear that u take into account ur addressees and expect them to answer. Without '요' it d be ambiguous: are u talking to urself or to someone else?

there are very subtle difference.... A: 그 사람은 고향이 어디예요? B: 그 사람은 고향이 어디인가요? (where is his hometown?) A and B, both are used well, but I prefer A (is his home seoul?) A: 그 사람 고향이 서울 아닌가요? (you doubt if you are wrong) B: 그 사람 고향이 서울 아니예요? (you accept that you are wrong) but it's not always this way, it's depends on person's way of speaking A and B, both are used well, but I prefer A