Choose a pitcher for convenience, taste and modest filtration. Choose RO when broad dissolved-contaminant reduction is the main objective.
Pitcher filtration
Pitchers typically use activated carbon plus ion-exchange or mineral media. They can improve taste and reduce selected contaminants while retaining much of the source-water mineral profile.
Reverse osmosis
RO uses a semipermeable membrane to reject a large fraction of dissolved ions. Finished-system performance should be evaluated under NSF/ANSI 58 or equivalent model-specific evidence.
Minerals and remineralization
RO also removes calcium and magnesium along with undesirable dissolved substances. Many modern systems add a remineralization stage after the membrane for taste.
An alkaline pitcher does not need to “undo” RO unless the user actually owns an RO system.
Ownership tradeoffs
Pitchers require no installation and create no drain water, but cartridges are small and frequent. RO costs more upfront and may require plumbing/electricity, but treats a much broader dissolved-solids problem.