When I was looking a couple of years ago, I had the exact same dilemma. Wanted the action of the Casio with the sound of the Yamaha. Casio used to be cheap tat, but they're much better these days. Yamaha are almost always good quality, will hold their resale value and are easy to get repaired if they do go wrong.
I had my problem solved by being offered a secondhand Yahama at a very reasonable price. It's been borrowed by a semi-pro friend for one or two gigs and he loves it. He wanted to buy it but I wouldn't sell and his wife is extremely grateful to me for that, lol.