I'll preface this by saying that I am also in the process of interviewing so I don't have the most experience, but I think it depends on what you are looking for long term. I spent a good amount of time at Mass Eye, and I loved it. It is definitely more academic leaning from what I saw. So if you want to work in academia, the name will take you far. That's not to say Iowa won't also do the same (name is also great), but in my experience, the residents at MEEI are set up to publish like crazy. That said, clinically speaking, my general impression (as limited as it may be), is that Iowa is stronger for residents from the clinical perspective. Also, Boston > Iowa City, but that is a personal preference.