It's a pad, but you don't have to set it up in advance. Arranger playing is ALL about spontaneity, otherwise you get better results with an SMF (and Mark/Jump). So, if you are the kind of player that DOES like to change up your chords each night, something like this makes each night as different as you want it to be, AND frees up your LH for things it could do better than slavishly repeating chord input.
Primarily, it is a feature for someone with a strong LH, that could be doing something else productively, or full pianists that realize Pianostyle Mode STILL does not quite follow REAL piano playing all THAT well (you have to make some adjustment to not trigger chords doing passing notes, etc.), or players of other, secondary instruments, or when you need to utilize the bender FULLY (rather than when your LH can spare it, which is generally NOT when you want to bend)...
It's definitely one of those things that, if you've never used one, you might not think too much of it, but once you HAVE, it's like losing an arm. With a chord sequencer, you can definitely think of yourself as a three handed arranger player!
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An arranger is just a tool. What matters is what you build with it..!