For a Shipping Container, Calcium Chloride Wins. For a Small Pack, Silica Gel.
The two are not equivalent. Silica gel adsorbs water onto a porous surface and holds about 25–40% of its weight; it is clean, reusable and ideal for small, sealed packs. Calcium chloride (BE DRY) chemically absorbs water and holds 300–600% of its weight, locking it into a leak-proof gel; it is the only practical choice for keeping a whole container dry across weeks at sea. As a rule of thumb, 1 kg of calcium chloride does the moisture work of roughly 10 kg of silica gel.
So the choice is about scale and duration, not which is “better.” A camera case, a barrier bag of electronics or a box of documents wants silica gel. A 40ft container of hygroscopic cargo on a 30-day voyage wants calcium chloride, because silica gel would saturate long before the ship arrived and could even release moisture back as the temperature climbs.