Use a faucet filter when the concern is sink water. Use a shower filter for shower chlorine or a validated shower-specific contaminant claim. Use whole-house treatment when the nuisance affects every fixture.
Faucet filtration
Bathroom faucet systems operate at lower flow and can use finer filtration without creating the same pressure drop a shower filter would. They are useful for face washing, brushing and other sink use.
Shower filtration
Shower filters must work at much higher flow and temperature. NSF/ANSI 177 is the relevant standard for free-chlorine reduction in shower filtration.
Products such as Weddell publish shower-specific performance documentation that should not be transferred to a faucet filter, and vice versa.
When whole-house treatment wins
If chlorine or chloramine odor affects showers, laundry, sinks and every fixture, treating one faucet at a time becomes inefficient.
Whole-house carbon can be more rational when the treatment objective genuinely exists throughout the home.