The only "correct" exposure reading is the one that provides the most accurate exposure for the medium being used - typically the camera will provide it. Typically, yo want the brightest exposure that will not burn out your highlights. That being said, an external meter can
be more "accurate", but that will be trial and error on your part as the meter is not reading the light coming through the lens as a TTL system does.
When I shot film (medium and large format), I used an external spotmeter, carefully metering the highest value in the frame and placing it at Zone VIII (three stops brighter than middle grey. One can also read and place the Zone II exposure value (three stops below middle grey). But both of these settings cannot be arrived at except through testing with the film and development you are using.
For colour work (specifically transparencies), I was careful to place the brightest value 2-1/2 stops above middle so as not to blow out the highlights - but, again, this is with a spot meter. However, for 35mm work, I relied on the very accurate camera meter (not evaluative, but still predicatable when use correctly with exposure compensation).
Flash and studio photography was generally done with an incident reading (light falling on the subject).
I can't imagine that a general purpose meter would give superior results to what you are reading through the lens once you have calibrated the camera settings with the film being used. I would suggest a good tutorial on basic light metering...