I'm a big fan of harken. Lightweight, strong, very helpful over the phone when I called. When I told them I bought a length of track from WM and didn't get the rectangular washers that it was supposed to come with, they said no problem, we'll mail some out to you. No charge.
Garhauer has also been very friendly to me. They make heavy duty products that look nice, however I do have a fiddle block that is getting some surface rust on it. Not sure why or how, but it is. Garhauer is also pretty heavy, and on my boat, that makes a difference.
I don't think you can go wrong with either one.
Merit 25 # 764 "Audrey"