Presumably those rays hit instantly
Bingo - All eye rays do not need to be described the same.
When I add a beholder the to the game, I give it unique eyes. I have dozens of central eye powers, and hundreds of eye stalk powers I've used over the editions. I've assembled beholders that have beneficial eye rays that use their powers to buff armies. I have beholders that are divine, natural, psionic and arcane in nature. And I have a wide spectrum of 'normal' beholders that can do a wide array of things, with mostly single target attacks - but the occasional cone, explosion or even summoning popping up.
GENERALLY SPEAKING (there are exceptions) - I try to give all beholders at least one eye ray that impacts each defense (AC, 6 saves). The remaining three might be duplicates of one of the defenses, or they might be things without saves (Power Words, Magic Missile type effect, Create Walls, etc...)
When I describe the eye rays of my beholders, I consider what a saving throw or attack might represent if I wrote it in a story. Con and Strength saves are often big blasts that hit instantly. Wisdom and Intelligence saves go directly into the mind. Charisma saves tend to create lights around the target instantly. Dex saves and attacks are described as shooting across the way. It is all about how you describe it.
