SE, you might want to stop in at a WM store, look thru the Harken & Schaefer catalogs (or the products themselves if they''re on the shelf) & determine for yourself how similar they are. One (IMO) major difference is that Schaefer has a clever way to permit the jacks to be drawn *aft* once the sail is tied off, avoiding hassles with the cover, slapping of the mast, etc.
I have not used them yet but have designed my own & will install them shortly. Why? For just the reason you mention: even if it''s only occasional, handling the sail on deck in a big sea is a safety challenge; making it easier makes it safer. If they weren''t satisfying to use by some sailors, why have I seem many, many boats with them thru-out the Caribbean...by which point the junk gear gets tossed?
Jack