I was researching Yamaha's FS and FSX keyboard mechanisms and as far as I know they're the same mechanism but the FSX uses some other kind of metal for the weights instead of lead. While looking throughout the history of the Motif series and various comparisons one thing kept popping up: "the Motif ES keybed feels better than the Motif XS (and XF assuming they use the same keybed)."
When asked why nobody was really able to answer but some people speculated that it was due to the lead weights in the FS mechanism of the ES vs the FSX mechanism of the XS/XF. That got me thinking. How can they feel different if they're weighted the same and everything else in the mechanism stayed the same? Is it perhaps the density of the lead? When did this switch happen and why? One person on the Motifator forums speculated that it was due to "ecological reasons" and that seems to be part of the reason why. My best guess is that since the EU outright banned its use in electronics in 2006 for "safety reasons" (so their signature environmental alarmist fearmongering) most manufacturers decided that it'd be cheaper to maintain one production line for the mechanisms instead of two for different markets and thus just eliminated lead outright. But was it worth it? Or rather, was it detrimental to how key mechanisms in general feel? I currently don't have an FSX keyboard (I won't be able to get my XF until April at the very least) but I do have a Korg M1 that uses the FS mechanism and I quite like it. I'm not exactly a pianist and I've never played a proper acoustic piano but as far as I know the FS/FSX is one of the better modern non-graded hammer mechanisms. Or at least people seem to prefer them to whatever modern Korg and Roland use.

 

The Motif ES6 had Yamaha's FS action. Arguably the most sold synth action ever (since it was used in both the Yamaha DX7 and the Korg M1 among other keyboards between the early 1980's and 2007) - Yamaha introduced the FSX action to replace the the FS when lead (weights) were banned (Motif XS was the first with FSX) - the FSX is a lead-free version of the FS action. The Motif XS6/7 and Motif XF6/7 feature the FSX action.

So in a true blindfold listening test you probably would not be able to tell the difference between the MOXF-series and the Motif XF-series, certainly playing the keys would feel different between the two series of keyboards. This is why when purchasing a musical instrument, it is so very important to try it for yourself... like trying on a new pair of shoes, the sales person always recommends you walk around the store with them - because only YOU can decide what feels best for YOU. And with keyboard players touch/feel and response is so very important.

MOTIF XF8 > Balanced Hammer Effect Keyboard (Initial Touch/Aftertouch)
MOTIF XF7 > FSX Keyboard (Initial Touch/Aftertouch)
MOTIF XF6 > FSX Keyboard (Initial Touch/Aftertouch)

Spoiler: High quality keyboards for first class playability

The MOTIF XF6 and XF7 use high-quality FSX keyboards with 61 and 76 keys, respectively. The MOTIF XF8 uses a BH (balanced hammer) keyboard with 88 keys. The FSX keyboard uses a newly-developed mechanism to provide a smooth touch that is both comfortable to play and responsive to your touch. It’s easy to play fast passages, including glissandos and trills.

It is also worth mentioning that the keys are very quiet.The balanced hammer keyboard is filled with the know-how and technology that Yamaha has developed producing full concert grand pianos and stage pianos. To make a keyboard with a piano touch that can still work comfortably with any voice, we took a graded hammer keyboard, which is a popular keyboard for electronic pianos, and adjusted it for use with a synthesizer: we balanced the keys to the same weight and made adjustments so that the synthesizer can support after touch and other features. While pursuing the real touch of a grand piano, we also provide a touch that is exceptionally suited to the performance of a multitude of synthesizer sounds.

Spoiler: Why is a graded hammer mechanism important?

Why is a graded hammer mechanism important? Since the sound is generated electronically with the digital piano, different weighting would basically not be necessary. After all, no hammer is thrown onto a string here. Rather, the tones are triggered by electrical contacts like an organ.

If you've never played an acoustic piano before, you probably won't miss a graded hammer action at all. However, if you want a playing experience that is as similar as possible to the piano, you should prefer a good digital piano keyboard with graduated weighting. If you want to learn how to use an acoustic piano, you have to learn and practice on an acoustic piano.

If you want to learn how to touch the piano properly, you should learn and practice consistently on a good acoustic piano. Nevertheless, there are digital pianos that simulate the nuanced interplay of hammer action and string vibrations very well. Hybrid digital pianos are at the forefront here.

Such upper-class digital pianos are even equipped with wooden keyboards and hammer mechanisms that are strongly based on the acoustic grand piano. You can expect top quality from hybrid digital pianos, which also costs a lot. The graded hammer mechanism is of course standard on these instruments.