Some hikers prefer to simply freeze a regular water bottle but that can be problematic.

Some hikers prefer to simply freeze a regular water bottle but that can be problematic. Which hydration option do you think is the best, bottles or reservoirs? https://www.nightgalaxy.com/blackhawk-hydrastorm-100oz-reservoir https://www.nightgalaxy.com/blackhawk-hydrastorm-nalgene-bottle