I didn't investigate Northwestern at all, so I can't do a proper comparison. Except for a handful of schools I had very little chance at getting into, I only applied to schools that were of the smaller city variety such as Austin.
Honestly, I think the decision comes down to location. Would you prefer to live in the big city of Chicago, or the more moderately sized city of Austin? Would you prefer Chicago winters during the school year or Austin summers during the break (when you could get an internship to migrate further north)? Do you prefer to have greater employment chances in Chicago or Texas?
Additionally, do you want a class size of 240 or a class size of 450? What is the cost difference? (Even out-of-state UT shows up as 8K or so cheaper per year on tuition alone, then probably another 5Kish for cost of living).
For me all of these questions except for the class size would give me a resounding yes for Texas. Add in the existence of my wife's extended family all living in the area and that's what pushed me towards Texas over many of the other schools I considered.