Nope! Each are both full GCSEs, so your school will choose for you to do Religious Studies A or Religious Studies B.
Religious Studies A allows you to study 2 religions (for the first paper) and then others for the ethics paper (second paper). [Personally, my school did A, so I studied Christianity and Islam for Paper 1 and Christianity for Paper 2]
But Religious Studies B requires you to study Catholic Christianity (for the first paper) and then possibly one or more religions (for the second paper).
It really doesn't matter which one you get, because either are full RE GCSEs. They're just different types with different ways of assessing and with different content.