Ive used both, with galv I get good quality certified class A galvanised 7x7 (typically sold as Travelling Irrigator Galvanised Wire Rope
, get 2070 grade) in the 10mm size as it seems to last about 10 years or so depending on use, at least in my experience in cooler waters with minimal care except from keeping chafe items away from it. For some reason 1x19 galv seems more prone to rust?
This lifespan is comparable to what most insurance
companies seem consider the recommended replacement interval with stainless. Though galv can get some minor surface rust showing around 5 years on the outer edges of the strands, it doesn't seem to get any worse while the majority of the galv coating is intact. Ive pulled stuff off a square rigger that was 30 or 40 years old and still near perfect, but it was wormed, parcelled and served, and regularly slushed with tar. Snowpetrel1 rig has had no preservative oils applied for about 12 years now and is still fine except for the stb lowers where the ratlines where seized on, trapping salt water
under the lashing, so the stuff does last OK if you source decent stuff. Some of my parents 6x19 wire has lasted 30 years with very sporadic treatments of linseed oiled or fishoil over the years, though its being renewed now with 7x7 galv. Use stainless for forestay that have hanks on them, though galv ones can work OK they get pretty dirty and stain your sails, and the hanks don't slide as well on them.
Uncivilised's chafe issue is valid, 7x7 is pretty rough, but black poly pipe over the chafe sections works well. It can be an issue to find the good stuff and find a company thats happy to do it for a yacht these days, and most yacht riggers don't touch it, and if they are forced to will usually put a huge overhead on it, and winge mightily about it during the whole process. It might be harder to get insurance
for the rig with galv, because insurance companies are generally stupid.
Be aware that some tangs and other fittings will not fit the swaged galv eyes in them, and the stainless to galv interface can be a minor problem, chewing away the galv faster through galvanic action.
7x7 galv stretches more than 1x19 which can effect some high tension noodley rigs badly but not the average cruising rig. Theoretically the thimbles can collapse under very high loads, but I've not seen it happen on a rig. There can also be a theoretical loss of strength in the clevis pin due to the rounded shape of the thimble, but again this doesn't seem to have been a problem on any conservatively rigged cruising yacht I have seen.
Still trying to work out how to do 1x19 galv on my new boat... Far too noodly a rig for 7x7 unfortunately. Need to break out my old marlinspike and see if Brion Toss's 1x19 splice is as much of a prick to do as it looks. Maybe 1x7 if and a molly hogan splice if I can find any of a reasonable grade.
If you go galv get the test certificates for the wire and the swaging work. probably even worth getting a sample break tested to help with the
The biggest issue with stainless at the moment is the amount of rubbish quality stuff being sold as a premium product. I've heard you really need to go to something like the very expensive compacted strand stuff to be sure it's not garbage. I think most stainless fails due to chloride stress corrosion
cracking not fatigue or overloading. Most galv looks pretty badly rusted by the time it's ready to break, plenty of warning with galv.
Saying all this Stainless is pretty easy, and it looks nice and shiny and you won't forever be dealing with comments or snide remarks from clowns who don't know what they are talking about.
Still down south? I spent a few days at the base during the resupply. Thanks for the great hospitality.