Yamaha, IMO, put a whole different level of investment into their styles than just about any other manufacturer. I honestly think this is the dividing difference between them and the others. In all fairness, hardware and sounds alone (no content), other arrangers are comparable (some of their sounds better Yamaha, some sounds Yamaha better them, etc.).
But with the styles, Yamaha leverage what they DO have to better effect. I wish more arranger manufacturers realized this. Only about 50% of the product is the hardware and sounds. At LEAST 50% is how good the styles are programmed. There are altogether too many arrangers where, when you get them OOTB, you have to go 'Why did they do THAT?! That string line is WAY too loud/busy/bright (or whatever it is)... who OK'd this?' and then you spend months undoing the laziness of the quality control.
Arrangers are about CONTENT. I've said it all along. Anyone that skimps on that part is doomed.
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An arranger is just a tool. What matters is what you build with it..!