I’ve done comparison testing with all 18 of the possible ambient / fill metering combinations on my Canon 20D and having been shooting seriously since the late 1960s using every meter type and method there is including Sunny 16. Regardless of the metering mode we select with our in-camera Through The Lens (TTL) metering getting the exposure correct is a three step process 1) let the camera metering make its best guess, 2) evaluating that guess, and 3) second-guessing the camera.
An axiom of metering is: The less one measures the more they need to know how to interpret the reading. For example a hand-held one-degree spot meter or the 5 degree metering spot in the camera can produce a precise measurement of light reflectance from that spot, but translating that reading into a correct exposure requires knowing that the indicated exposure will simply reproduce the spot as gray.
