I guess my favorite is the Hoover Convertible, but really, I haven't used one of the Eurekas. They just didn't seem to be common.
My mother used to clean a clubhouse for extra money when I was little, and in the closet they had a tan plastic Hoover Convertible without headlight. There was a plastic grocery bag hanging on the handle with belts, bags, and the manual.
She never used the Convertible because she had her own vacuum to use, so if she was really busy, I would get out the Convertible and run it. I seem to recall it was very quiet and made a low grumbling sound.
Another time I saw a Convertible in the thrift store, and later saw what seemed to be the exact machine in someone's trash. I picked it up, but was too scared to plug it in. I'm having trouble remembering the details. I want to say it had an orange hood, but I think it used type A bags. Maybe it was one of the last models that were red, and it was much newer than I thought.
I did see an older Eureka in the trash too, but it was missing the bag. I took it apart for fun.
I haven't really seen either type in about 10 years or so.