Your old carbon pile controller probably needs adjusting; there is a very good
blog post from Tammi on this. A new pedal should in theory have more gradual and precise control (...but, like in your case I know it doesn't always work like that. I have yet to find the explanation for it). The old controllers have a bad reputation; turn hot, uneven speed control, etc., but it's usually a case of having them adjusted and serviced properly. I have developed a feel for my old Singer button controller, and it works well.