EGPWS uses cautions and warnings via a combination of aural and visual displays; aural and visual should not be considered separate.
Cautions, 'amber level' alerts are intended to aid awareness and trigger corrective action as necessary; the words 'caution' and 'alert' are often interchanged.
Warnings, 'red level', require immediate action.
'Terrain' represents a particular threat and has related cautions and warnings, 'sink rate' is a terrain related caution and thus requires corrective action. If a 'sink rate' caution progresses to a 'pull up' warning, then pull up.
Any caution represents an unexpected situation, being somewhere or having done something not previously considered; thus always act.
A 'pull up' warning from any source or in combination with cautions is always actioned as a red level action.
IMHO any note which introduces an exception - day, VMC, etc, adds to the complexity of operations. Who and how are these judged, added workload, more time ... the same time as required to pull up.
I recall a CFIT accident in the Southern Med where the aircraft was VMC above cloud and the PM reported being visual with distant high ground (mistaken land mark); there was intermittent vertical contact with the sea. GPWS commanded a 'pull up', the crew hesitated and the aircraft hit the top of high ground still climbing.
This scenario was replicated in the simulator and evaluated by twelve senior line pilots from different airlines, they had some expectation of a warning. Six of them did not clear the hill; indecision, slow response, slow pitch rate, low pitch angle.
Fortunately EGPWS provides greater alerting times and a graphic display, but there are still situations requiring prompt action without distracting exceptions.
http://www.icao.int/safety/fsix/Libr...plus%20add.pdf
Add to the above, the crew who declared 'visual' with the field and descended early, they didn't see the radio mast - no obstacle mode fitted; but a transiting senior captain in the cabin did at eye level.
A few choice words during the debrief.