First boat had a ShoreLand'r (not a Shamrock), current (Shamrock) has a Boatmaster. I wouldn't hesitate with either of these brands, but I can say the Boatmaster is an excellent quality trailer. Aluminum, bent I beam construction, stainless fasteners, stainless brake lines, just an all around good trailer.
I can verify their customer service is fantastic. I bought the current boat used, 1989, with same year trailer. The rating sticker on the trailer wasn't legible so I contacted Boatmaster about the specs. They gave me the model number, complete specs on exactly how that trailer was originally built. I emailed them multiple times, with prompt responses to all inquiries, keep in mind I had never given them a penny, but they were still happy to help me. I ended up needing new axles for the trailer. I contacted them and they were able to ship me 2 new axles, that were a direct fit, with a new stainless steel hardware kit. Axles went on perfectly and I couldn't be happier with everything.
If I was in the market for a new trailer, I probably wouldn't even contact another manufacturer. That is my experience.
I have zero personal experience with Load Rite, but have friends with them and haven't heard any complaints.
Twenty years later I continue to use the Magic-Tilt trailer with bunks purchased new from Marine Warehouse Center in Wilmington, NC for 1977 Shamrock 20’ Open Fisherman (910) 799-1277. Only modification was I changed out leaf springs to torsion axles when replacement leaf spring were needing replacement every couple of years. The original springs lasted 4-5 years.