Face-on is harder
Seeing a galaxy's spiral arms clearly sounds like the ideal view. It is also the one most likely to defeat you.
The same light spread over more sky, which is exactly the wrong direction.
The brightness trap
Surface brightness is the number that matters, and it is merciless. A galaxy seen face-on spreads the same total light over a much larger apparent area than the same galaxy tilted nearly edge-on. The result is a lower surface brightness — fainter per square arcsecond of sky — even if the two objects would measure identical on a photometer aimed at the whole disc.
The eye, working in low-light conditions with no colour and limited dynamic range, responds to surface brightness rather than total brightness. A big, faint smear of grey is harder to hold than a compact, brighter streak. Edge-on galaxies have concentrated their light into a narrow band; face-on galaxies have spent it across the full disc, and the sky background quietly competes with every part of it.
M74 in Pisces is the canonical punishment. Total magnitude around 9.4 sounds reasonable. Surface brightness around 14 magnitudes per square arcminute is brutal. On a mediocre night at a mediocre site, a telescope that would show dozens of other objects simply finds nothing where M74 should be. Experienced observers learn to dread the low-surface-brightness warning before they even go outside.
On a mediocre night at a mediocre site, a telescope that would show dozens of other objects simply finds nothing where M74 should be.
The spiral arms themselves compound the problem. In a photograph they are vivid, high-contrast, unmistakable. At the eyepiece, the arms are only marginally brighter than the disc they wind through, which is only marginally brighter than the background sky. Dark adaptation and averted vision help, but they cannot create contrast that the object does not provide. What you get, on a good night, is a round softness with a slightly brighter core — no arms, no structure, just confirmation that something is there.
This is not a failure of skill or equipment. It is geometry doing exactly what geometry does. The photons are present; they are diluted. The practical lesson is to treat a face-on galaxy's listed magnitude as a starting point and its surface brightness as the real test. A galaxy two magnitudes fainter but nearly edge-on will very often be the easier object.
The spiral arms are real. The photographs are accurate. But the view through glass is a different measurement of the same thing — and sometimes what it measures is absence.