confused-mathguy

I am in a very unique situation and I dont know what I should be doing. I have two offers to choose from. One is a fully funded PhD in Mgmt from RPI. The other is PhD in industrial engineering and operations research from UT Austin which is not funded. The RPI PhD will take only 4 years to finish. The UT Austin one will take 5 years atleast and I may not have any funding during the first year of studies. UT Austin is very big name. I am not sure how big the name is for RPI. I need to make a decision quickly because I have accepted the offer at RPI and in case I want to decline I need to do it as soon as possible. I am interested in emperical research and I have a professor to work with at RPI. I will be really grateful if one of you could give me any insights on the same.