Here’s an interesting video to show how different the modern tuning system of Equal Temperament sounds in comparison to earlier just and well-tempered tunings (a reminder that what we call ‘in tune’ today is vastly different to what previous generations would’ve considered good tuning):

Piano TEMPERAMENT comparison. – YouTube

Of the other tuning systems I’ve tried while tuning pianos, Thomas Young temperament and Werckmeister III were my favourites for the dissonance they added to certain chords (which better conveys the emotion of the music), and the variation between key signatures (something sadly lost in modern tuning). My go-to “Factory Default”, safe piano tuning system as a piano tuner Leeds is Equal Temperament at (preferably) A440 or, if that’s not possible, A435, A432 or A415. This is what the customer’s ear expects and it is guaranteed to be satisfactory. For personal taste, my acoustic piano at home is currently tuned to Thomas Young temperament, as I play a lot classical and like the home keys to sound more pure and for dissonant chords in Chopin and Bach to sound closer to the composers intention.