Originally Posted by defjef
Keel stepped can be leaky, but they don't need rigging to stand. A deck stepped is more like a guyed radio
tower. Cut the stays and the tower falls down.
Everything Jef says, except many larger keel stepped masts will collapse under their own weight without rigging holding them "in column" (straight up and down). They do that by bending and breaking, not just falling over!
If everything else was identical, the keel stepped mast is stiffer. To compensate for this, the deck stepped mast has to have more stiffness "built in" with diameter or metal thinkness or else it has to have more fancy rigging.
For an offshore
cruising boat, given two boats that were identical in all other respects, I'd chose the keel stepped mast, but wouldn't make it a real big reason for selection of one boat over another. If you are cruising canals with low bridges, keel-stepped might not even be a useful option to consider.