Musical notation provides a kind of symbiosis between composers / arrangers, and players. If you want to work, you have to read standard notation. If you want your material to get played, you have to write it in standard notation. And learning any notation to the point of sight-reading it is prohibitively difficult for most people, including good musicians who learned without reading.
Experiments with developing new notation tend to involve a cooperation between the composer and willing players, often in an academic setting. It's also a wide open field for electronic and computer aided music, where sight-reading might not be an issue at all.
I'm not saying traditional notation isn't useful, I'm saying it's unhelpful if you're trying to understand how music actually works.
All that to say I think they're both conveying similar pitch information and take a similar amount of effort to ready correctly. Piano roll doesn't convey rhythmic information and that's where I think piano roll falls short as a method of straight notation.
Traditional notations are obsessed with pretending there are only 7 notes when there are in fact 12. Accidentals and key changes are obfuscated.
Similarly, key changes are explicit in sheet music but hard to see on a piano roll without careful inspection.
Likewise, when a musician sees a run of adjacent notes without accidentals, they immediately know what to play. They don't need to inspect each one in turn to determine how many semitones it lies from the previous note. Likewise, when a composer wants to write such a run, they can just draw some black dots in a row. They don't need to squint at a grid and select the correct rows each time.
To sum up, traditional notation is uses a form of compression that makes reading and writing diatonic music easier.
Taking this even farther, some systems of music notation compress things even further and don't explicitly list all of the notes to be played. For example: figured bass, basso continuo, or even just chords that accompany lyrics. In fact, even regular sheet music doesn't usually precisely represent of duration of all of the notes. Some notes are sustained and bleed into others, some are meant to be played strictly in time. Human interpretation is an important part of the process.
On the other hand, the piano roll is a MIDI editor. It is a great way to tell a computer exactly what to play, but it is not easy to read quickly and it is impractical to print or write by hand. Both forms of notation have advantages and disadvantages but it seems to me you haven't spent enough time with the standard notation to fully appreciate its advantages. In other words, the piano roll notation might be your blub language for music. [1]
Because the most important thing is the actual semitone intervals, and the standard notation hides them and gives them weird names like augmented fourth (it's just six semitones, just call it that). And it names the 12 semitones based on the c major mode even though that's only one of about 50 modes/scales/keys you might want to use.
In relation to the staff, pitches in standard notation are just as "proportionally spaced". Instead of squeezing in black keys, you have to squeeze in accidentals, but then accidentals are an extremely useful way of "showing how chords work", especially in the context of progressions in tonal harmony, which a piano roll gives you no meta-information about. It's less intuitive only in that you need some study to parse it fluently, at which point you gain the advantage of being untied to the layout of a particular physical instrument.
In any quest to "understand how music actually works", as soon as you take some baby steps beyond the basic alphabet of intervals, a piano roll visualization is going to hold you back.
I looked at some music mapped onto this layout. The layout allowed for speedy recognition of lone intervals and simple chords, but no more so than standard notation, and it was far worse than standard notation at showing any higher level musical content (the harmonic function of those intervals and chords in the context of the piece or a progression, polyphony and independent voices in general, counterpoint, organization of rhythms and cross rhythms, phrasing, larger compositional structures...). Also, because it's just a homogenous field of repeating piano octaves there is much less to positionally anchor the eye on as it reads through, like a staff with ledger and bar lines would provide to a fluent sight reader. All this musical meaning is stripped away and to reinstate it would be a case of painstakingly decoding the piano roll rather than just fluently reading the music.
I can see how this layout is really useful in a DAW for MIDI input and editing. As for learning the absolute basics of harmony, yeah it's accessible, if you can't be bothered to learn the basics of standard notation. After which point it's a dead end.
I looked at some music mapped onto this layout. The layout allowed for speedy recognition of lone intervals and simple chords, but no more so than standard notation, and it was far worse than standard notation at showing any higher level musical content (the harmonic function of those intervals and chords in the context of the whole piece or local progression, polyphony and independent voices in general, counterpoint, organization of rhythms and cross rhythms, phrasing, larger compositional structures...). Also, because it's just a homogenous field of repeating piano octaves there is much less to positionally anchor the eye on as it reads through, like a staff with ledger and bar lines and key signature would provide to a fluent sight reader. All this musical meaning is stripped away and to reinstate it would be a case of painstakingly decoding the piano roll rather than just fluently reading the music.
I can see how this layout is really useful in a DAW for MIDI input and editing. As for learning the absolute basics of harmony, yeah it's accessible, if you can't be bothered to learn the basics of standard notation. After which point it's a dead end.