Rusty,
My first HO engines and cars had the Mantua hook loop couplers. I lived with those for a couple of years, then went to dummy knuckle couplers even though the NMRA couple was a standard from almost every supplier. I never liked them. So when Kadee first announced their new coupler (slightly different from today's version, I started to convert my models to Kadee.
I'm now using Kadee on most of my O gauge 3-rail freight cars.
RAY