Not a scientific sample by any stretch of the imagination, but for the specific Harvard-Alabama pair, you might would find something at http://talk.collegeconfidential.com/university-alabama/1549857-what-schools-did-your-child-pass-on-in-order-to-attend-alabama-p1.html which could lead you to find how anyone who went to Alabama instead of Harvard ended up doing.
I have to say, though, if any of my kids got into both, Harvard would be nearly full pay according to their NPC—and no, we’ve got a good income, but not that good—and Alabama would be about $10k. The decision has effectively already been made—which means my kids will never be ones that turn down Harvard for someplace else, because they’re never applying to Harvard. That invisible pre-creen of applicants skews the ability to make comparisons, too.