In this case “better” is usually means better for acoustic players. Fact 2: For amplified, bluesy ballsy tone, “better” is worse.
Fact 1: There is no such thing as a mic element designed for harmonica players.
Every microphone uses an element that was designed for more general purposes.
The reason vintage bullets are so popular is that their frequency response typically falls off at as low as 3000 Hz – even though some humans can hear as high as 20,000 Hz. And it is a good harp mic for playing acoustically, or for avoiding a distorted input signal for other reasons such as playing through an amp modeling pedal.
As a rule, the more expensive a mic was when new, relative to other mics of its vintage, the better it performs as a general purpose mic.
To engineers, this means it has better frequency response (able to “hear” higher and lower sounds), flatter frequency response (no particular frequencies are made significantly louder or softer), and/or more “headroom” (the ability to tolerate higher sound pressure levels without distorting).