Arguments often arise about whether it is better to use four or five-line (modern) notation for Gregorian chant. The advocates of modern notation are usually people who have had some kind of musical training, and they have even been known to suggest that beginners should start with the modern notation then move on to the "more difficult" four line scores.
If you can't read music anyway there is absolutely no point whatsoever in bothering with modern notation for Gregorian chant. It just adds confusion. Start with the four-line scores.
The traditional notation was invented for the specific purpose of writing down the chant, so that people could sing it consistently. The notation is tailored to the chant. The groups of notes, called neumes, give a very clear indication of how they should sound, illustrating the pitch, length and dynamic in a compact and concise way with each neume on the stave directly above the syllable it refers to.
So what is wrong with modern notation?
Several things. Five lines are obviously more difficult to read than four. The words are all spread out, which does not help with reading and singing it as a text, which is the primary purpose of the chant, as an embellished form of text reading rather than a musical performance. Modern notation also ties the singers to a key, which may not be the one they would like to sing in, since it might be too high or too low for their voices. And there are many subtleties in the chant which are easily shown in the original notation but which cannot easily be portrayed in modern notation, with the result that the music itself suffers and the refinements get lost. Ultimately, modern notation destroys the chant.
So is traditional notation difficult for beginners?
Not really. Gregorian chant is graded. A single note is shown as a little black square. That could not be simpler. The groups of notes are best learnt a few at a time, starting with the two-note neumes and then going on to the three- and four-note neumes. It is useful, though not essential, to learn the names of the different groups. If you are a novice, do not be scared, just start at the beginning with the simple stuff. If you are teaching, please don't bamboozle your pupils with chant written in modern notation.
How to read chant from a score