The biggest differences between all the marine hardware companies and their products seems to me to be the budgets of their advertising departments.
The most crucial consideration in purchasing hardware and rigging is proper sizing and material. All the products have safe working loads and the companies stand behind their claims. They also all have a useful lifespan. Garhauer used to actually stamp an expiration date into some fittings.
If you buy a block that is rated for a certain load from any of them, then you can count on them working as advertised.
There will always be differences. If something weighs less, they you may have to compromise longevity. If you want bearings, you may have to compromise working strength. If you want strength, you may have to compromise weight etc.
Advertising works, it sells products. The more you advertise, the smarter you advertise, the more product you sell.
You can create an impression that your product is superior to another by advertising it to richer people and then charging more money for it.
"If it costs more, it has to be better".
Because a company spends a fortune on advertising in all the glossies, doesn't necessarily mean that they produce the best product for the money. But it does mean that they have to recoup the money they spent for the ads.
So, the only difference between the offerings of Harken, or Fredericksen/Ronstan, and Garhauer, or Barton, are their advertising budgets???
Uhhh, I don't think so.... :-)
I believe once you get upwards of 40 feet or so, the superior performance of a brand like Harken really starts shining through... As one of the OP's original questions was regarding a traveler for a mid-boom sheeting setup on a 50-footer, I think whatever premium one might pay for Harken over, say, Garhauer for such an application, would be money well spent...
Not all of us who favor hardware from a manufacturer like Harken are rich guys who have been duped by clever marketeers... Some of us may simply choose it, because we may feel it's the best... :-)