Wow, tough question. There are tons of factors to consider. How big is the financial differential? How big is the brand differential? How important is the money to you? How difficult will it be to finance your education without the scholarship or lower tuition? Certainly an unrated school for free wouldn't be worth giving up a top ten school. Nevertheless, there are many closer and tougher decisions.
Look at the schools' relative ratings not just overall, but in your specialty. There are several schools that rate lower overall but are exceptionally strong in areas such as international business or product management. In those cases, if the strength is in your field you are giving up less. What do you plan to do with your MBA?. If you are going home to run a family company, brand is less important. You simply need to ensure that the curriculum covers all the areas needed for success in your business.
Look at the graduating salaries. US News publishes averages for the top schoolsl. If your "brand" school shows an average salary $40,000 a year higher than your scholarship school, giving up a $20,000 scholarship can be a smart financial move.
Try working backwards. What do you want to do when you graduate? Who are your dream employers? Where do they interview? You may find that the chance of landing your dream job is just as good at the lower ranked school. Geography may be important. A school with a lower national rank may have more drawing power in its local area.
In the end, only you can decide which makes the most sense for you educational, career and financial needs. just be sure you look at all the options.
Tani Wolff