my view is that Synthesizers are pro. because you can make your own sounds "anyway" you want it.you can add effects and double it and put some filters on it and you can even now sample with high more sophisticated ways on Synthesizers.some of the arranger keyboard offer sampling and effects too but not as pro. as the Synthesizers.but they(arranger keyboards) give you a feeling of you are doing what a band can do.

that's how I think of it.Synthesizers for creating new sounds and arrangers for back ground(styles) for known(common) sounds.

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vic:)