Energy wise, they last up to 60% as long as a block of ice in a plastic bag wrapped in a thin layer of foam so it doesn’t frostbite you. The benefit is the ability to recharge them in the fridge or even in a cool place instead of the freezer.
also those hand warmers seem like they’re bad because they’re tiny not because their chemistry is flawed.
you know those noisy portable AC units with hoses? if you have a balcony or porch this may be an ideal option for you since the noise goes outside and the heat goes inside with minimal noise.