I would suggest that a well travelled intelligent individual would have established enough memory and perception of many landings, to recognise if one may have been harder than the others ?
Maybe, maybe not.
Have you ever thought about the perceived difference in firmness of a landing depending on where you're sitting in the cabin? Any pitch change during touchdown can greatly influence the experience.
For instance, if the aircraft starts a pitch down just before touchdown this will be experienced by the pilots as a reduction in G, but by passengers and FAs in the rear as an increase in G. Add to that the G loading on impact, and what might feel as a smooth landing up front could be perceived as a firm landing in the back. This could also happen the other way around.
Do you always sit in the same seat row? Is this right above the wheels so the above mentioned effect is minimised? (But never cancelled, because on touchdown the point around which the aircraft pitches changes from an aerodynamic one based on the CofG to a fixed one based on the gear, which changes as the oleos compress). Do you have information about the CofG, the attitude and more importantly the rate of change of attitude of the aircraft on touchdown? Even the pilots don't have all that information readily to hand.
A 'hard' landing is one after which engineering inspection is required. That is the definition. Anything else is a firm landing and according to the quotes I supplied earlier is as Mr Boeing intended it to be. That doesn't mean that some are not more firm than we wanted them to be, but this has nothing to do with the operator of the aircraft, be it LoCo or Legacy.