Well, the camera meter is generally excellent, but it has pros and cons.
Pros - it is a TTL meter, it sees and meters the same view whatever lens sees, be it narrow telephoto or wide angle.
Cons - it is a reflected meter - it only sees the light reflected from the subjects colors, which is a lot of light from light colored areas (tending to underexposure), or it is not much light from black or dark colors (tending to overexpose). Whatever issues you may have with it is probably this reason. See
How light meters work
A hand held reflective meter would have two cons, the same reflected issues, plus it is always a fairly wide view, regardless of the view that the lens sees. The reason in-camera meters are so popular is because they are so effective (and convenient). Maybe not always precisely accurate (but it is not really about accuracy, more that your goal and their goal is not the same thing).
But a hand held incident meter sees and measures the actual direct light falling on the subject, it measures the light, not the subject. All pros, no cons. This is totally awesome for multiple flash, but it works anywhere, in continuous light too. Except an incident meter cannot be in the camera, we need to walk to the subject and meter the light aimed back at the camera, which is sometimes awkward outside the studio. There is just one Sun, so it really does not matter where we stand then, except if shadows are involved, we may need to get into the shadows.