I think that both Yamaha and Casio are very good in their respective targeted markets.
Speaking as someone who had been in music retail for 30 years, who plays out, loves music and who teaches, I will discourage anyone from buying a Casio who is a beginner or any other level. Why? Many adult hobbyists are lucky to manage playing with both hands. Most will be started with single finger chords and most will continue with that. They want to have fun making music, they're not going to Carnegie Hall. Even if they think they want to learn 3 and 4 fingered chords and eventually buy a piano and play it fluently, it will not happen if their life depended on it.
So, I feel in all the discussions on this particular topic that I have ever seen, I do not recall that the most important subject has been touched on. Most hobbyists will be playing with one finger in each hand. Then when the minor chords come along they play with 2 fingers.
Yamaha and Casio have different easy play fingering systems. I always try to help a beginning student by having them get a Yamaha because they become accustomed to one fingering system and a OS that is similar on all of their instruments. If they want to upgrade, they can get a $3000 Tyros 2 or a $15,000 Clavinova at some point, and their playing will not be disrupted. It makes for much easier sailing.
How far up can one go in the Casio line? A few hundred dollars? Then what? They want to upgrade and then they have to attempt to learn a whole new easy play fingering system? I will not put my students through that extra agony.
Most adult hobbyist will never sequence, care about playing with drawbars and will have to put in plenty of effort just to understand the basic operation of the arranger controls, which is why they are interested in the first place. They want to be able to play live real music.
While these comments are leaning more towards older adults, I still believe the same thing for children and younger adults. Why subject them to one way of learning, and then want to change them?
Scott
http://ScottLMusic.com