Weiser,

These types of questions are great way to start "heavy artillery fire" from three different directions (i.e. Roland, Yamaha and Korg 'followers'). :-)

You just mentioned three TOTL models of arranger (although G-70 is a bit older then E-80, but has some advantages, and disadvantages over the newer model), of major arranger producers (of course Wersi and Mediastation owners will disagree), and each one has it's own strengths and weaknesses as well.

Apart from different specification, each of the mentioned models have specific sound, and arrangement differences, and in order to choose the one that suits You the most, You have to listen to it, because sound is personal experience, and something that sounds wonderful to me, might sound as 'load full of crap' to You, or anybody else (and vice-versa). So, whatever answers You get (no matter how objective or subjective they where) still might get You in wrong direction, and I am afraid You are going to have a little bit of investigating, searching, reading, and listening, until You find the correct answer.

Good luck, and I hope You will find the keyboard that suits you the best.