The trouble is, once you decide to use the highest quality sounds, the best available samples, the most expressive keyswitching, well, even a GB is paltry. You look at the sizes of some of the better GIGA instruments, just ONE can max that GB out, and still need more!
GIGA, Kontakt, most of the modern VSTi samplers stream from HD, which no modern arranger other than the MS can do. So, in fairness, you are going to be still mired in older sample sets, as all the latest stuff relies on streaming (modern sound designers have just about given up on trying to make samples space efficient). Personally, if I was looking for something right now, I think I would prefer a Muse rather than deal with a built-in sampler, particularly as how relatively barebones the Ketron voice architecture is. Kontact can do a LOT more with the samples than an Audya can...
If, as you say, you are not shooting for live convenience, why not use the tool with the most flexibility?
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An arranger is just a tool. What matters is what you build with it..!