Of the 3, I've only used FinalWriter and AmigaWriter. I think Final Writer is the more intuitive of the two to use.
However, my main Amiga Word Processor is still ProWrite 3.3. I started using it years ago on my first Amiga (A1000). It was rock solid. And still is on my OS3.9 Amithlon machine. I guess I got used to it over the years.