This search in PubMed will get you articles from the primary clinical literature on infant equipment.
I found the following:
http://www.ncbi.nlm.nih.gov/pubmed/21929486 - Just a letter to the editor, a simple case report. Not, in my view, evidence.
Consumer Reports says that sling-type carriers have been more frequently recalled and there seems to be anecdotal evidence (which isn't actually evidence) that doctors don't like the slings.
The American Academy of Pediatrics thinks the front-carriers are best for babies up to 6 months and that the "backpacks" are for babies more than 15 lbs...and they seem to emphasize safe USE more than a particular brand.
The way I used this info for our own kids was to avoid the bag-sling type of carrier in favor of the front-mounted or back-mounted, then asked our pediatrician for any thoughts about what cautions to take that may not be covered by the manufacturer's instructions.
If in doubt, I always say, ask a pediatrician you trust.