Fino vs oloroso sherry
Fino develops under a layer of yeast called flor, giving a dry, fresh and often savoury style. Oloroso develops through oxidative ageing without that protective flor layer during its main maturation, commonly bringing fuller body and nutty depth.
Oloroso is not automatically sweet: check whether the wine is dry or a sweetened style. Serve according to the particular sherry rather than treating all fortified wine alike. Amontillado provides another useful comparison because its development includes both biological and oxidative stages.