Hi! Good question. It's been a topic of debate for a bit. Here is my take: I would borrow in the first year unless you have easy access to a cheap emergency loan down the road.
Longer Version: Interest rates are LOW right now so I would grab a fixed loan in the first year. (not all of them are fixed though) Yes, you will pay more in interest but you can deduct it on your taxes (since your income will dip) and get perhaps 10-20% write off and also lock in a low rate in case there is inflation coming our way. Moreover, your loan will paid out in 2 installments (one in Aug/Sept and one in Jan) so the interest bill wont' be huge but you are paying for flexibility. You can also keep your other money in a conservative stock/bond portfolio or i-Bonds to off-set that interest disparity, though that adds to your tax bill too but in the second year, you will likely only make your internship pay which will be $20-30K tops so investment/interest income is not going to add much.
My second thought would be that, everyone always runs low on cash during business school - there are recruiting trips, peer pressure to fly to Iceland to for a long weekend, and all kinds of opportunities you won't be able to resist and perhaps will never get a chance to experience again. Having a reserve of funds, you can choose to forego a loan in the second year or you may consider getting it.
Finally, do you know when you will get a job out of business school? Nobody does and it is nice to have a cushion of something in case things don't work out when you graduate and you need to spend 3 months looking for a job and not to have drive for Uber at the same time, focusing on recruiting instead.
Ultimately if you had an easy way to borrow money, then you don't need a loan in the first year but since most of us lack that ability, it gives extra flexibility and a safety play allowing to lock in a low interest rate too.