Sorry to add an answer to my own question, but I have just found the following information from Canon to be useful:

>The trouble when using exposure compensation with evaluative metering is that you don’t know if the metering has already compensated for the conditions. If it has, and you dial in even more exposure compensation, then the exposure will be wrong. Equally, if you assume that the camera has got it right, but it hasn’t, then you will also have a badly exposed picture.
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>The solution, as with so many things photographic, is experience. After a while you will learn to recognise the types of scene which evaluative metering handles well, and those that it does not.
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>When you change to a different camera, you will have to learn all over again, as the number of metering zones can change the results.
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>Centre-weighted metering takes a reading from all of the framed scene, but with more emphasis on the central area. It was one of the main metering modes on Canon FD cameras, which came before the EOS range. Centre-weighted metering was originally included in EOS cameras to help FD users make the transition, but seems to have become a permanent feature.
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>Unlike evaluative metering it makes no attempt to analyse the scene, so you can apply exposure compensation in the knowledge that the camera has not made any adjustments of its own. For this reason, centre-weighted metering is often better than evaluative when you know that some level of exposure compensation is needed.

Source: [Canon Professional Network][1]

  [1]: http://cpn.canon-europe.com/content/education/infobank/exposure_settings/exposure_compensation.do