I have both types and love both! The thing with computerized machines is that they make sewing easier and more enjoyable and you're not limited by ANYTHING. The sky is the limit for your imagination. The down part is that they're not made nearly as well as older, mechanical machines and are much more costly to buy and repair. Old machines are true workhorses and need no babying. They are dependable and sturdy. The negative is the lack of bells and whistles and they are not able to do the fancy work new, computerized machines are able to do.
Really, it's like comparing a 50's T-Bird with a new luxury Mercedes Benz. Both are wondeful machines but have their pluses and minuses. It all depends on what you want.