Big 3 Credit Rating Agencies: Structured Finance vs US Public Finance

I currently have offers from 2 different CRAs, one in Structured Finance and the other in US Public Finance. Which would best position me for IBD or Credit Research at a bank in the future?

I'm conscious that Corporates would be best for credit research, and public finance is somewhat relevant to a lesser extent. What I'm not clear on is how relevant Structured Finance is to IBD; I've seen two analysts mande the transition so far to debt capital markets but not sure if they are outliers and would love your insight.