My favorite two are the ones I play now, the Korg PA4x and the lowly Roland EA7. Each as it's strengths and neither is perfect, though the Korg comes very close.
Having said this, there are so many great arrangers available now and it's wonderful to have all these great options.
Yet none of them is perfect
Which will probably never happen..
I think we live in a great age for keyboardists too
With the pa5x just around the corner, and probably some new Roland products too