Both can create cold water immersion. The biggest difference is how you get the water cold and how much work is required to repeat the experience.
A chiller can hold or return water to a selected temperature without adding fresh ice every session.
Many systems combine circulation with filtration and sanitation features.
Convenience usually comes with more equipment and a larger upfront purchase.
A suitable tub and ice can be enough to get started.
You need enough ice to reach the desired temperature each time, unless your environment keeps the water naturally cold.
Temperature can vary as ice melts and ambient conditions change.
Frequent use makes automation more valuable.
Portable tubs can be easier to store while rigid systems can feel more permanent.
Both approaches require clean water and a safe setup.