Quick take
For households drinking several liters per day, a good RO system is usually the better long-term value. Bottled water still wins for portability and emergency backup.
Long-term cost
A household buying cases of bottled water every week can spend hundreds or thousands of dollars over several years. A countertop or under-sink RO system shifts more of that cost upfront, followed by predictable replacement filters.
Control over treatment
With a home RO system, the owner can choose the exact treatment technology and inspect model-specific certification. Bottled-water treatment varies by brand and source.
Convenience tradeoff
Bottled water requires storage, transport and repeated purchases. RO requires filter changes, cleaning and sometimes electricity or plumbing.