I think Ketron has a way to make it sound pleasing easily; their instruments usually have a smaller selection of sounds (far less than 1,000 sounds), and a lot of the sounds are less customizable than e.g. Korg's ones, less individual, but very pleasant and ready to play, often with a sampled vibrato.
In addition, probably ballroom styles are one of the genres Ketron is specialized in; saxophone sections are perfectly matched to a Glenn Miller tune etc.
That would be my explanation why you get along better with Ketron.