Yes, I think metaphors are more subtle, whereas similes are something of a bludgeoning implement. One could describe a political or sporting fiasco in metaphorical terms as a train crash or go for something along the lines of 'like a train that went off a cliff. ' Like most forms of communication, a lot depends on context. I think similes work well for emphasising the ridiculous. If I used the phrase 'about as much use as an ashtray on a motorbike,' there's an element of the absurd about it.