I've been looking at the manual and data list for the PSR-E473 and PSR-EW425, and here are my impressions, so far. Keep in mind, these impressions are subject to change based on discovering more information and hearing the keyboards in a live setting.
First of all, my disappointments...
Same style engine as on the E433 (and maybe even further back) -- No dedicated drum fill button -- Cannot do fills without also changing the style part. No improvement here in the past 10 years or more?
Same 6-track sequencer as on the E433 -- Still approx 19000 notes (which has been more than enough for me, but you'd still think there would be some advancement after nearly 10 years), still no editing capability.
Still not able to set the sustain pedal to also sustain the left side of a split keyboard.
Still no portamento (at least none that I could find in the manual) -- Even though Casio has had this since around 2018 for this type of keyboard and even though Yamaha includes it in the PSR-I500?
Still only 32 registrations. Really? Again, no improvement in nearly 10 years?
Some improvements...
64 note maximum polyphony.
An increased number of sounds -- though like in previous models, be aware that a certain number of these sounds are generated by automatically adding a pre-selected dual-voice sound, meaning that these tones cannot be combined with another tone using dual voice, because dual voice is already being used.
Hammond B3 type effects (key click and "leakage") for some of the organ sounds -- BUT ONLY ON THE EW425. Similar organ sounds are available on the E473, but without the key click and leakage effects. Why couldn't Yamaha put these effects on both keyboards?
Style freeze -- It has been possible to program in a style freeze to each individual registration -- at least on the E433 on up -- by simply making sure you select the "song" button before setting up and saving a registration. This causes the registration to NOT save style data, and therefore let the currently playing style settings to continue after selecting such a registration. Now, it appears you can save style data to a registration for when you want that feature, but then tell the keyboard to ignore the style data by simply turning on style freeze. With style freeze on, you should get the same effect -- the ability to change registrations to change sounds during a song without suddenly changing the style and tempo.
Transpose freeze -- A long overdue function. On these keyboards, the transpose setting is saved to a registration. This means that if you're playing a song with a singer that needs to sing the song in a different key than the one you normally use, you could use the transpose function, but any time you select a different registration to change keyboard sounds while playing, you'd change the transposition setting again. Now, it looks like you can set a transpose setting and then freeze it, so that you can then change registrations without changing the transpose function.
Direct buttons on the panel to shift the tone up or down an octave.
Some significantly interesting features...
The numerous DSP effects now available, the fact that there are two different slots/settings for DSP, and that the second one of those slots can be set to effect the whole keyboard or just a particular section, such as the style background.
S.Art Lite -- This has now been around for a while on the E373/EW310, so most of us know what it is, and it's now available here on the E473/E425. The sustain pedal can be set to be an S.Art Lite activator, which would allow this feature to be used during two-handed playing.
Motion effects to alter the tone dynamically while playing. It looks like this can be used to add modulation, thereby adding a feature that has been missing on these keyboards -- but it can also be used for various other effects, as well.
Sample pads -- It looks like this can give something similar to multi-pad functionality, depending on what kind of samples are stored in the pads. As far as I can tell, the sample will not transpose based on the chord being played with the style. And curiously, the manual states that using the samples uses notes in the available polyphony. I would've thought that samples would have their dedicated memory separate from the polyphony of the normal sounds, but this does not appear to be the case.
So, I'm not sure how I feel about these keyboards. After nearly 4 years since the previous model, I was hoping for improvements in things like the style engine, sequencer, and number of registrations available. But it looks like there are a lot of sounds, effects, and DSP options. The important things that cannot be determined by the manual, however, are the key feel and overall tone. So, I'll have to wait until I can actually play these keyboards live to determine whether I'd want to buy one.