I choose the Yamaha.

Please elaborate further ...have you played each/or...?
The Fantom intrigues me ..

Yamaha has the fm engine which I like a lot. I don’t know much about the fantom as I am not really interested in a Roland. Yamaha and Korg sound more pleasant to my ears.

Well with these worstations in genera is all about making your own sounds/music in any way you desire...workflow on the Fantom is amazingly easier then previous to creat music.

I know they are all great for music production but personally I will go for the montage because I like that sound the most. But I am dreaming because I never can afford one of these 4

The Kronos has an equal FM engine... its also 8op.. even more versatile (mod7)
The Kronos also has other engines that outshine the montage..
However, the montage is much easier to opperate..and is a dsp powerhouse..

Roland is on a homerun with the Fantom..
But only reached first base so far, but looks like the ball might make it over the wall

MEDELI

I choose Kurzweil. I had a couple and I love the sounds....But, If I was to try all of them today...who knows.....I sold mine because they were more for a stage musician in a band...not a one man band performance, as we have discussed....

As far as I know has Medeli no workstation but who knows in the future. However they do have a very interesting new arranger I am still interested in the akx10.