That's not how it works. Kaido is more feared because he is a threat to far more people than Dragon. Everyone in the New World either fear the Yonko, or directly oppose them, while they're generally apathetic towards the WG and the Revolutionaries.
Kaido is well knows/feared in these areas: 1)New world 2) Marines 3) First half of GL(Most of people don't know about him).
But in case of Dragon: Whole GL,Marines and Normal civilians from almost every kingdom are aware of Dragons name.
Dragon may not be a bad dude but still WG considers him as a criminal hence almost everyone in OP world fears him.
OT: Dragon is the most feared.