They are pretty much interchangeable, however there are a few subtle differences. Here's a great link that shows the difference between -body and -one. Quick Summary: 1. ‘Someone’ is used if we don’t know the person and there are many people to decide from. The use of ‘somebody’ is when we refer to a person but in a narrow amount of selection. 2. ‘Someone’ sounds personal, exclusive, and formal. ‘Somebody’ sounds vague, informal, and distant. 3. ‘Someone’ is more appropriate for formal writing whereas ‘somebody’ is slang, casual, and unofficial. 4. ‘Someone’ is pleasing and likable; ‘somebody’ lacks engagement and appeals only in limited occasions. 5. Both words have indistinct proper usage; both have minor differences. Link: http://www.differencebetween.net/language/differences-between-someone-and-somebody/

Somebody, someone = кто-то, Anybody, anyone = кто-нибудь, Everybody, everyone = все. Nobody, no one = никто. По-моему нет разницы между двумя вариантами.

I think they are equal in meaning but subtle diffenent in use.