Mostly size. Ordinary shooting stars are grain-of-sand sized, and what you see is actually the superheated air that they displace coming in at 10+ km/s. Something slightly bigger, like a rock a few cm wide, can cause a blinding fireball.
Speed also counts. It can range from 8 km/s (a "stationary" object, relative to us, falling into Earth's gravity well) to about 70 km/s (something in a retrograde orbit in the Earth's plane). That's a factor of almost 80 in energy to be dissipated
> Meteors are the result of the high-velocity collision of meteoroids with Earth’s atmosphere. A typical visible meteor is produced by an object the size of a grain of sand and may start at altitudes of 100 km (60 miles) or higher. Meteoroids smaller than about 500 micrometres (μm; 0.02 inch) across are too faint to be seen with the naked eye but are observable with binoculars and telescopes; they can also be detected by radar. Brighter meteors—ranging in brilliance from that of Venus to greater than that of the full Moon—are less common but are not really unusual; these are produced by meteoroids with masses ranging from several grams up to about one ton (centimetre- to metre-sized objects, respectively).
I think if you consider light pollution around populated areas and the fact that most people don't spend much time looking at the sky carefully, most of the shooting stars actually noticed by most people are larger than sand, probably more like tiny gravel than sand.
Speed also counts. It can range from 8 km/s (a "stationary" object, relative to us, falling into Earth's gravity well) to about 70 km/s (something in a retrograde orbit in the Earth's plane). That's a factor of almost 80 in energy to be dissipated