not sure which one
If you are using it strictly in the US, I would keep it on LTE/CDMA. The phone would remain pinned on those two bands.
I noticed it works good on my phone. I don't want the phone to be hunting for different bands than it needs to.
There are different opinions on this, if you have a weak signak , being on global setting might help in grabbing a signal to establish a decent connection.
Try them both and see how the phone performs.