Either one will work just fine, and the battery drain will be virtually identical between the two.
Global works exactly the same as LTE/CDMA, except that when all all Verizon-compatible LTE and CDMA connections are lost, it will then try to look for a compatible GSM network in addition to LTE and CDMA (because with a lack of connection to Verizon's network, it thinks you could be traveling internationally). The Verizon SIM card isn't compatible with any U.S. GSM network, so it won't end up connecting to anything. The only time that could be different is for people who live along the Canadian or Mexican border and who are in range of a GSM network that operates outside of the U.S. that is a Verizon roaming partner.
In LTE/CDMA mode, if you lose service from Verizon, it will keep looking for Verizon-compatible LTE and CDMA service.
The only time there will ever be any differences in how the radio behaves is when you lose Verizon-compatible service completely. If this happens on a regular basis for you, Global mode might drain your battery slightly faster because it's searching for three potential networks as opposed to two, but it won't be that big of a difference. Verizon has the phone programmed to default to Global mode so that the phone will work more easily internationally since it's advertised as a global device. If it was programmed to default to LTE/CDMA, you can be sure there would be several complaints from novice travelers who don't know to switch the network mode. It's just easier for Verizon to default to Global since the impact on performance is virtually non-existent for most people.
So, for most people, it really doesn't matter which mode you have the phone in. Both will perform exactly the same for almost everyone pretty much all the time.
