If you want references to show the difference in health between breastfed and formula fed babies, you can find some of them here .
The SIDS thing is more controversial, although the bare statistical facts are not in dispute (ie that formula fed babies are at a higher risk of SIDS). In the UK, the Foundation for the study of infant deaths has always avoided saying anything more than 'breastfeed if possible' (I think that's the term they use) without putting it more strongly.
Their view, as I understand it, is that it is difficult to separate out socio-economic factors from the feeding factors in the research, especially now that SIDS is so rare in the UK (mainly since the back to sleep campaign).
Sleeping position is more easy to distinguish in research. Your social and economic circumstances do no affect how you place your baby to sleep.
But other factors are not so clear cut.
SIDS is associated with so many factors - smoking in pregnancy, smoking in the family, low birthweight, prematurity, previous illness and infection - that are also associated with poverty and deprivation.....and formula feeding is also associated with poverty and deprivation.
So it's all mixed up, and not all research is powerful enough to teaze out the different strands.
Some countries do state very clearly that breastfeeding is protective against SIDS and they have this on all their campaign literature (New Zealand, for instance, unless they have changed recently).
The Foundation blotted their copybook in the last couple of years by taking sponsorship from one of the formula manufacturers - I don't think this relationship continued for more than a short time.
Other health issues - gastroenteritis, chest infections and so on - show up very clearly as being influenced by feeding method. Because these conditions are more common than SIDS, it is easier to get a study where you can control for socio-economic factors and make sure this is what your results are showing ie that the difference between babies is the feeding, not the fact that they are more or less middle class.
In fact, there is some good work that shows breastfeeding can reduce inqualities in health - see here and this is actually the main reason why government are making efforts to support it (means less cash spent later on).
None of this justifies anyone feeling criticised or distressed for using formula milk, by the way. None of this means mothers who use formula are bad mothers - as if! None of it predicts what will happen to an individual baby either.
But it is tedious in the extreme to be continuing to argue whether breastfeeding makes a difference to infant health....of course it does.