Ships designs are good for a variety of strains - they’re built to get tossed around in storms after all.
Also about the sails comparison - I think the kites are retractable and redeployable, ending up with a variable, lower ship profile.
Water also has super high drag forces - it sounds efficient to counteract the constant water drag using constant air drag instead of constantly burning fuel.
Giant kites could pull ships across the ocean – and slash their carbon emissions (www.cnn.com)