I've noticed there is also fierce debate between digital pianos that are based on sampled sounds versus modeled. I believe most Roland digitals are modeled with Fourier series, while all/most of their competitors are sampled (not sure about Nord). That said Pianoteq is a popular after market VST that will bring a very convincing top tier modeled sound to even a low end digital piano.
Exception if you're going to travel with it. Built-in sounds save you on setup time.
If you use a decent quality open back headphone, I feel like this is even more true, because the onboard sound becomes irrelevant.
One of the things I plan to do is connect my iPad and laptop and play around with all the newer piano VSTs that I’ve missed since being away from that world for about 10 years. Sadly Kawai pianos don’t work as USB audio interfaces, so you can’t pipe the VST output back into its onboard speakers. The Roland pianos all support this feature, as do I believe most or all Yamahas.
My absolute favourite is the Nord Grand, but it's a little too expensive.
Was really pleasurable, also wistful, taking my son to try them out. We could just hang out in this large room in a retail store in the middle of NYC for a few hours, he just playing whatever was there. Sometimes other kids would drop in too. That kind of relaxed vibe now incredibly rare.
And though I can hear and feel the music, I can't make it, never learned. Don't have time and space to do it now. Really glad he is getting it into his brain at a young age.
You could go Kawai VPC-1 which is just the controller, and then connect it via MIDI to whatever you like. That way, you get a wooden action without paying for the sound engine (I've got my VCP-1 connected to a CP Reface):
I looked up the VPC-1 and while I probably would pay a bit more just to have speakers and a sound engine - the weight difference is interesting. It's 29.5kg for the VPC-1 vs. 17.0kg for the ES920!