My 3 pianos, including two with fully weighted keyboards and a Yamaha C5 Grand, all have sustain. It's the right-hand pedal, or have I missed something?
Sorry I didn't explain myself well. I can't in a word or two.
On the piano, I hit a note, and I get an attack, then the piano note which, depending on the pitch, either slowly or quickly decrescendos to silence. How long do any of the highest octave notes on your piano sustain?
On my sax I can hold a note for roughly one minute, depending on the pitch and the volume.
During the time I'm holding that note, I can make it louder and/or softer again and again. I can alter the pitch to a degree using my lip pressure on the reed. I can change the tonal color by changing the shape of my oral cavity or the degree of breath support in my diagram. I can add some distortion by adjusting the muscles in my throat, and I can 'flutter tongue' to get a tremolo effect.
I can't do any of that on the piano.
With FX pedals, I can do some, but not all of these on an electric guitar.
But it comes with a price. I can only play one note at a time on the saxophone.
Every instrument has its own capabilities of expression, which are governed by the physics or electronics of the instrument itself. That doesn't make one better than the other, just different, which is why we have a symphony orchestra instead of dozens of violin players.
I started on drums. Percussion, but not melodic percussion like piano, or marimba. In retrospect, that was a great instrument for a person who went on to be a rock/blues/jazz/Latin/country musician plus one who writes BiaB styles.
I wanted to play euphonium (baritone horn), but in 7th grade, all the instruments for the school were rented. Then the tenor sax player's family moved. I wanted to play anything melodic at that time, so when the band director asked who wants to play sax, I guess I was more enthusiastic than the others. Even though it wasn't my first choice, it was a good fit, as I not only got first sax in the all-state band every year, but I got section leader, which goes to the first alto by default. Better than that, I got in rock and roll bands, and I am making a career in music. I couldn't do that with baritone horn.
I played in rock, blues, or jazz bands after school, and since every songwriter doesn't have the good taste to put a sax part in every song. I learned bass, keys (mostly synth), and rhythm guitar (simple barre chords) from the other guys in the bands.
That allowed me to switch instruments on stage - good show biz. I could go back to the drums and let the drummer come out front to sing, I could switch to guitar, bass, and/or keys, and got a lot of experience playing different instruments live. Through the years I taught myself flute and wind synthesizer. Finally, after years of playing just barre cords on the guitar I decided to get serious, and not only learn other chord types, but to play lead guitar and melodies on it.
This also helps me write BiaB styles. Who knows better about the role of each instrument, and how they interact with each other to make the music than one who has experience playing each of those instruments for a living?
Back on topic…
So with decades of practice on multiple instruments, I find guitar easier than piano. But that doesn't mean guitar is easier than piano for everybody. My experience, my physical advantages/limitations, and learning the things I learned at the age I learned them shaped my preference. Someone else might be different.
So IMO the definitive answer to which is easier or more difficult is - It depends on the musician.
Insights and incites by Notes ♫