For the type of music that the vast majority do here at SZ, the arranger is probably the better tool (and probably why we choose it).
The problem starts when you try to do anything from the last 20 years or so... The nature of loop based music doesn't translate as well to arrangers as you might think. Arpeggiators are NOT merely dumbed down styles. They do things that the note lookup tables of arrangers don't do. They also don't revoice as you transpose, or move to another chord. Plus, much of the loop production DOESN'T transpose at all, while other elements do.
In truth, if you aren't involved in contemporary music production, you really have no idea of the issues that make the arranger an unsatisfactory tool for the job.
Now, that's not to say for LIVE performing, the arranger can't outshine the WS. As many of you know, I have preferred live band gigging with my G70 over my Kurzweil and Triton for years. The WS is of course FAR more flexible in sound creation, but all of them are utter pigs to quickly create setups on the fly, to create splits and layers, to route effects and controls, and do it fast enough to not interfere with the song. In this area, WS could learn a LOT from arrangers.
But bring them into the studio for modern music production (much of which is done inside the computer these days anyway), take the pressure of instant gratification away, and the arranger struggles to compete. If you are doing mockups for dated types of music, then yes, they can get the job done quickly, more quickly perhaps than a WS, but if you are producing hiphop, dubstep, or any of the bewildering explosion of types of music I am sure virtually none of you listen to, the arranger is a buggy whip in a smartphone world.
But, bottom line is, they are all simply TOOLS. Arguing ad nauseam whether your spade is the best, or the merits of Phillips vs. straight head screwdrivers somehow seems absurd. Don't we have more creative things to do?
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An arranger is just a tool. What matters is what you build with it..!