Okay,
So a long-time Yamaha fan here, I bought the Kronos over the Montage- purely from a synthesis point of view for me- the vast array of sounds fit my desires. Key words being "my desires".
Also key (pardon the pun), is the fact that I already have a Yamaha EX5R and FS1R, along with a VL1-m, DX-7MkII, & SY-77.
I also have a fully loaded Roland XV-5080, so I have plenty of polyphony, plenty of meat & potatoes ROM stuff, as well as true analog synths, software plug-ins & Logic and other DAWs.
I felt like I was missing the Korg flavors in my arsenal. If I didn't already have an EX5R & FS1R, you can bet I'd be all over the Montage.
As far as build quality goes, Yamaha can't be beat. The fact that I have so much "vintage" Yamaha gear AND that it all works, is a testament to Yamaha's quality and engineering. I also play Yamaha Trumpets and Flugelhorn.
Consistent build quality is amazing from Yamaha- second to none.
I know money doesn't grow on trees (wish it did,lol), but if you can save your pennies, buy BOTH 🙂 - they are different, that's why they both exist- look at them to complement each other.