For starters, the T5 will be at least double the price of a BK-9. So any comparison to a BK-9 will be like putting a Camry up against a Ferrari!
Secondly, there isn't enough information out about the T5 to make an informed comparison. Of course, this won't stop the usual breathless speculation and Christmas-like anticipation, even from those probably already aware that will never afford one of these overpriced arrangers...
At it's price, it had BETTER be miles ahead of anything else! TBH, at the moment, compared to a PA3X, I don't see what it has that makes it so much more expensive. Other than the might of Yamaha's marketing behind it, and the somewhat blind partisanship of many of its players. Watch them line up in the next few weeks to praise something they haven't yet laid eyes on!
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An arranger is just a tool. What matters is what you build with it..!