For the phrasal adjective and adverb meaning comprehensive, versatile, in every respect, or completely, all-around is preferred in North America, while all-round is the more common form throughout the rest of the English-speaking world. Other than the spelling and sound, there is no difference between them.
In either form, the phrase is usually hyphenated when it precedes what it modifies—e.g., an all-around success; an all-round good guy. It is unhyphenated when it follows what it modifies—e.g., it was a successful day all around; he is a good guy all round).
And of course, the phrases all around and all round have plenty of other uses—e.g., men all around the world are choosing Acme deoderant; music was all around us–where they are not hyphenated.
Hernández, who has played in 33 test matches for Argentina, has great all-around skills. [New York Times]
But despite the well-trodden ground, it finds its own patch thanks to an up-to-date landscape of economic hardship and all-round criminal incompetence. [Guardian]
He was described as an all-around nice guy. [CBC.ca]
The regional grand solution is going to require compromises all round. [New Zealand Herald]
On an afternoon that contained much frustration all around, the Denver East senior defensive back picked off a pass and returned it for a touchdown. [Denver Post]
Andy is an all-round footballer, but because he is 6ft 3in and one of his strengths is his aerial power, everybody dismisses the ability he possesses on the floor. [Irish Times]
Pennsylvania dance instructor and all-round ogre Abby Lee Miller has a rather unkind way of ranking her troupe of tiny dancers after each performance. [The Age]