Originally Posted by snic

This might be specific to the phone and/or its settings. Or perhaps to the use of a carrier that has spotty coverage in some parts of Brazil. I was in Brazil for a month, and I visited several regions (including both the Argentina and Brazil sides of Iguacu Falls, where I also noted multiple switches between 3 countries' networks) and never noticed any difference in phone battery life. But I also had pretty reliable 4G coverage in cities, and 3G pretty much everywhere else. It may be that because Fi is specifically designed to work on multiple networks around the world (i.e., it's designed for roaming), switching among them is optimized so there is less searching and battery drain.