I have had the Worthington trailer you are talking about (WU-6412) since 1999. Mine is the HD model, 2990 GVW, 2" pressure treated flooring, 16" pressure treated sides, and a 5' 2000lb rated ramp. It has a been a great trailer. I replaced the tires last year- other than that, I have never even changed a light bulb. The trailer has hauled tractors, mowers, ATV's, garbage, building materials, etc.
I just ordered a 6418THD model (18', 7000GVW, tandem axle, stowable ramps) due to the new tractor I bought last year. I looked at many models, but came back to Worthington.
I stayed with the 2" lumber floor, I felt the aluminum would be too slippery, and I worried about denting it with some of the uses I may have for it. The benefit for the bi-fold ramp is that it carries lower for visibility, and it catches much less of the wind.
I hope you enjoy your trailer as much as I have enjoyed mine.
Will