The advantage of LTE/CDMA is that if you lose connectivity to cdma, the phone won't activate GSM to try to find a signal (which won't work in the us anyway - Verizon has no roaming agreements with GSM networks in the us). If you normally always have signal it shouldn't make a difference.
I always switch to LTE/cdma unless I'm outside the country, though.
For some weird reason, I get better reception with global turned on opposed to LTE/CDMA. Tested in same low reception location.