I bought a fish scale first because at the time that was the only thing available I could find for weighing 50 pounds. The digital luggage scales came later. The problem I had with the fish scale was that you had to lift your luggage very smoothly. If you had the slightest jump the little tab that marks your weight would jump as well and give you a false weight. For me this got aggravating and when the digital scales came out I jumped on it because after you lift your luggage and hold it for a second or two you will hear a beep and the weight will be displayed for a few minutes even after putting the luggage down.
The digital scales don't cost all that much more then a fish scale and having used both I found the digital scale much handier. I saw the Balanzza digital scale at TJ Maxx today for $15.
Shak