Recently I have been asked the same question. Tried to look for the answer, an English linguist and grammarian George Yule says there's " [...] little difference in meaning. Others adjectives used like this include: easy, exciting, great, hard, impossible, interesting." (p.144; Yule, Oxford Practice Grammar, OUP 2006)
I've also been thinking of it as Yule tells of a 'little' difference. So I have come to conclusion that there must be some kind of explanation. I think the first one may refer to a singular situation, a specific situation; while the other to repeated ones.
I agree with Matilda the second one is better at the end of conversation.