The difference is that even if the first statement may be true (and without knowing what the source data was and where it came from it's difficult to say), it doesn't preclude "intelligent" people from believing. The second statement doesn't allow that provision.

Anyway, the same Telegraph spells out some other concerns with the article you cite:

http://www.telegraph.co.uk/news/uknews/2124100/High-IQ-linked-to-atheism-claim-attacked.html