The descision of which arranger keyboard has the best acoustic piano will depend a lot on the genre (rock, jazz, latin, blues, new age, etc) of music you play, as well as the style of keyboard playing you use (solo piano, full/split keyboard mode, etc).

I think the piano sound on the Ketron SD1 & Roland VA boards really shine for rock, r&b, blues and contempo pop. Both provide plenty of body to cut thru the mix, though the SD1's piano sound is a bit darker.

For straight ahead swing & jazz standards, I prefer the Technics KN keyboard's lighter 'transparent' sounding piano. If you want to play in the comping style of an acoustic jazz pianist (in full keyboard mode), then this is a best choice.

For 'best overall' acoustic piano sound suitable for the widest variety of music genres, my vote goes to the Yamaha 9000pro.

Scott