Apples and oranges. If you are thinking of the way DiMarzio rates pickups, the 200 and 150 would be milliVolts at a specific frequency with the pickup set a specific difference from the string, and probably a specific
string guage. Hopefully you have gathered that this is a relative spec, for comparison only. The resistance is just that, the resistance of the wire wrapped around the bobbins and is a function of the wire guage and number of wraps. This is not 6 or 12, but 6K or 12K ohms (kilo ohms) meaning 6000 or 12000 ohms.
To answer your hypothetical question, 200mV would be greater than 150mV so pickup A would be louder for the specific set of circumstances that the test was performed at. However, the frequency responses would be different so the pickups would sound quite different, depending on wire guage, type and strength of magnet, etc... A Steve's Special has a higher output that a Tone Zone by the specs, but a TZ can sound louder because of it's hyped midrange. Actually, all of the high output
DiMarzio pickups are so close in output that there isn't that much difference, frequency response will have more to do with how loud a pickup sounds.
This wasn't meant to confuse you, but pickup design has to take into account alot of parameters. Basically, what happens is a conductor (string) vibrating in a magnetic field (created by the magnets and screws) generates a voltage in a coil of wire in the same field. That's the Electronics 101 explanation. Now to translate that into cool sounds for guitarists takes as much technical knowledge as it does black magic (okay, experience and trial and error).
EMGs do this on a smaller scale, then amplify the generated voltage through an amplifier circuit. Like a small pickup with its own built in booster.
Make sense,
Roger
