As has been stated Cedar is softwood, and is pine - which is what most other hives are made from. Deal is just a generic term for pine.
The rate a which a tree grows determines the density of its wood. The rate is determined by environmental conditions, water, light, and more importantly temperature...
Thus a Norvegian Spruce (softwood) growing in Nothern Scandinavia (above the artic circle) grows considerably less in any year than an Ash (hardwood), Alder (Hardwood), Beech (Hardwood) growing in southern England, or for that matter teak (hardwood), Mahogany (Hardwood), Purple Heart (hardwood) growing in the equatorial belt.
Even Western Red Cedar comes in various grades, and the best grade is mountain grown, and in Eurpoean terms comes from the Balkans.