Le futur proche vs le présent

Question

Ron gave some good guidance on j’arrive, but is there general guidance on when to use le présent and when to use le futur proche? For example, it seems to me that « Je vais partir d’ici deux heures » would be just fine, but based on the lesson maybe that’s not the case?

Answer

While Ron did give good guidance, it's really not done this meticulously in practice though it sounds good in theory. In practice, there seems to be overlap between the two and there is no official rule specifying a time frame when you have to switch from one to another. Every French speaker seems to decide for themselves. If the action is not pretty much immediate (like screaming "I'm coming!" as you run towards the ringing doorbell) but within 24 hours, both the future proche and the present seem acceptable.

Of course there is a subtle difference.

Demain, il arrive à dix heures.---Tomorrow's he's arriving at ten o'clock.

Demain, il va arriver à dix heures.--Tomorrow, he is going to arrive at ten o'clock.

Answer

But what is the difference in meaning?  How would a non-native speaker know when to use which?