For a pretty good comparison of most of the software and hardware pianos (no arrangers, but you can post yours there if you feel up to it), try this site;
http://www.purgatorycreek.com/index.html

Follow the link for Digital Piano Shoot-out.

They provide the MIDI file to play through your keyboard, so you can sit and compare.

Personally, the G70's The Grand X patch (from the FantomX) provides the best arranger piano I've heard. I've got a K2500 with the piano daughterboard in, and while it's VERY good, the G70 GrandX patch is warmer, has greater dynamic range and, due to the G70's VERY low latency and killer action, a much better sense of 'connectedness' to the sound.