What's the difference between round and around?

Taken from oxforddictionaries.com:

"Are round and around (as preposition and adverbial particle) interchangeable in all contexts? In many contexts in British English they are, as in she put her arm round him; she put her arm around him. There is, however, a general preference for round to be used for definite, specific movement (she turned round; a bus came round the corner), while around tends to be used in contexts which are less definite (she wandered around for ages; costing around £3,000) or for abstract uses (a rumour circulating around the cocktail bars).In US English the situation is different. The normal form in most contexts is around; round is generally regarded as informal or non-standard and is only standard in certain fixed expressions, as in all year round and they went round and round in circles."