The answer to this question is often muddied by semantics.
For this reason, 'structure' & 'cover' should be defined at the onset, so everyone is on the same page:
'Structure' refers to the configuration and composition of the bottom terrain, it's essentially immovable
and relatively permanent. Elements of structure include bottom 'projections' (ridges, bars, humps, reefs ~),
bottom 'depressions' (ditches, potholes, gullies, channels ~), and changes in substrate (clay, sand, loam, silt ~).
On the other hand, 'cover' refers to more portable and more temporary objects that are found upon structure.
There are 3 basic forms of cover: 'weedy' (soft), 'woody' (firm) and 'rocky' (hard).
In the grand scheme of things, 'structure' reigns supreme. Nevertheless, it would be a mistake to 'always' regard structure
as more influential than cover. Prey fish and predatory fish both seek a similar habitat, a menu that evolves
from natural balance. So what's more important, structure or cover? The answer can vary sharply
from one lake to another lake, but as a rule-of-thumb, the commodity in lowest supply holds the greater worth.
Roger