Robinw, there is research on these issues, see for example a good survey of women several months after birth - full text is here www.biomedcentral.com/1471-2393/1/4.
It's called Achieving sustainable quality in maternity services ? using audit of incontinence and dyspareunia to identify shortfalls in meeting standards.
It shows that incontinence and pain on intercourse are measurable after-effects of pregnancy and birth, whatever the sort of birth, though overall, instrumental delivery with forceps or ventouse (as opposed to normal, and section) seems to have the greatest effect.
I am sure there is stuff on episiotomy and/or perineal damage as well. One problem with the sort of comparison you're after is that it is not simple to compare sections with all other births - sections can be elective or not, and vaginal births can be of many different types, each one of which may impact differently on health and recovery.
The authors of that paper make the point that women are not always given the right sort of help with these problems, or even the opportunity to report them.
I suspect that after-effects of birth - of whatever sort, section or not - tend to be under-reported, and the fact that problems can go on for months or more is also under-reported.