This is probably echoing the comments made above, but I strongly recommend taking the UMN PhD offer as well.
Of course, I can understand your interest in learning from some of the top scholars at Chicago to boost your CV for the next cycle,
but even with 50% aid you'd be incurring the following according to the website.
"A one-half tuition award, on the other hand, puts your total costs for 2018-19 between $48,919 and $52,919 (depending on whether you choose to live with a roommate).
If staying through August, you should add $4,300 to $5,667 to your total costs."
That's $60K at worst and 48K at best.
If you don't find your experience at UMN all that enjoyable or fruitful, you can exit after one year for other opportunities with the first year of stipend,
or as noted above, take the MA after two years.
Of course, the choice is fully up to you, but if I were you, I'd go to Minnesota!
Last, but not least, congrats on the admissions offers you have!