I think the root cause of many bugs is a design that has become too brittle (or was brittle in the first place) - the symptom of the design's deterioration is generally more bugs appearing, because the whole thing becomes more difficult to maintain, etc.
So, E & C emphasises fixing the symptoms, rather than trying to fix the root cause, as refactoring claims to be able to do, or at least help with.
So, in terms of productivity, refactoring should enable the whole thing to be maintained easier, and this should lead to less bugs, so less need for 'edit and continue', and therefore greater productivity.
With 'edit and continue', you'd continually be patching up holes in the boat - you might do that more efficiently, but it would still be patching.
I think thats what the refactoring guys would say anyway, and I tend to agree with them.