The Harken lazy jacks were on my boat when I purchased it several years ago. After the first sail I promptly removed them. Unless you are directly into the wind when raising or flaking the main they WILL get caught on your battons....guarantee. The jacks will also require that you modify your sail cover to accomodate the set of lines on both sides of the boom. Sure, you can pull all of these lines forward and store them against the mast as some do however if you do this all of these lines will slap against the mast when the wind is blowing. Suffice to say I think that they are more trouble than they are worth, that is unless you have a 40 footer or larger. I sail a 34 foot sloop (high aspect design) and the main sail is just not that difficult to handle. I single hand the boat all of the time, when its time to drop the main, the autopilot takes over to keep me into the wind and I simply do the rest. Concerning your question "Harken vs. Schafer" I think there is very little difference.
FYI I know of several people on smaller boats (under 40 feet) that have removed the jacks for the very same reason. "Resist the force Luke"
I disagree with denr; on a bang for the buck basis, lazy jacks are great. i have the wichard system; costs a little more but the quality is excellent. using this system you can deploy and "un" deploy the lazy jacks as such it is not necessary to modify your sailcover or to have your battens catch in the system while you are raising the sail. the only time they are deployed is during the main drop. i sail a nicholson 345 with a huge old main. if you sail is new and crisp, lazy jacks are less necessary. if i did not have them the sail would pile onto the deck. good luck
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?
I designed and installed a set of lazy jacks that used a continuous catch line. The slack was always on the low side, and gravity held the hardware away from the sail so there was no chaffing of the sail. Mine was installed on a Southern Cross 31. During four years of cruising, they never banged, got in the way, or did anything other than make sailing a lot easier. I have installed six of these on different size boats. Lazy jacks work if you know how to use them. If they are hanging on the sail while you are trying to raise it, the "jacks" are too tight. If you loosen them, gravity will pull the lines towards the mast and get them away from your battens.