I had a Pacific Aluminum trailer on my last boat, a Fountain. I really liked that trailer, great for salt water and towed nicely.
My current boat came with a rectangular steel tube trailer, looks nice, but I would never choose such a trailer. When I go to the ocean I launch at King harbor where they have a hoist, so I don't have to put the trailer in salt water. Steel tube trailers rust out in fresh water too, it just take longer (10 years or so). I have a friend who had a steel tube trailer that was pressurized, it eventually got a leak and rusted out. Bottom line if you are boating in salt water and have a choice get an aluminum trailer, they are well worth the money. My next trailer will be aluminum.