Originally Posted by
B747-437B
Maybe not for service, but as far as battery life goes there is a huge difference between a roaming sim card that is searching for a network versus a local sim card that logs on to its home network. I had full 4G roaming data coverage on VIVO in Sao Paulo, but my battery barely lasted 3 hours before I had to bring out my spare battery pack and eventually my emergency solar charger to top up enough juice to summon the Uber that got us home. In Rio however, I went entire days on a single charge. Iguacu was the worst though as the phones kept jumping between Brazil, Argentina and Paraguay networks - but I had the car charger to keep me topped up during the day.
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.