I'm in a similar situation. Im currently at a tier 2 school (that is bordering on tier 3) but I will be on law review next year. Im considering transfering to a tier 1 (where I wont be on law review).
If big firm is what you're looking for, it may be better to stay. If you're top of your class with law review, you should/may be able to land one of those jobs (although, many employers may overlook law review in favor of a big name school applicant). However, I spoke with someone who, after law school, worked in DC and a big firm. He said that your first employer will often look at law review, but, it may get trumped by a bigger named school. Additionally, after your first job, no one seems to really care what your rank was or if you were on law review, or if you were on moot court. Instead, it seems that the questions pretty much begin and end with: "where did you go to school and tell me about your last job"?
Its a really tough call. Good luck with it. Let me know if you find out any more valuable insight (some others on this board have helped a lot).