By evalu8tor's numbers each merlin will replace 1.5 SK, which means that in combat each loss equates to a comparable loss of 1.5 aircraft. Capability is not the only issue the numbers game is also valid in a full scale war. The inability to replace modern combat aircraft quickly could easily lead to total loss of capability.
I recently read a nice piece written by an American office who travelled in eastern Europe at the end of the second world war. He commented on how he kept comming across a destroyed german tank with half a dozen burnt out Russian tanks around it. We all know who won that encounter. Numbers win in the end, wasn't that the basis of Montgomery's victory at El Alamein.