So in our imperfect world, which is more important?
Frankly, neither.
The most important thing is how the system as a whole sounds to YOU in YOUR room.
Buying equipment based on specs can be a very expensive endeavor. You might find the perfect set of specs and save a few bucks by buying it on audiogon, but if it doesn't sound good you you then it doesn't matter how much you saved.
Take a look at the article on Wikipedia about damping factor and read some of the external links in that article. That should give you a good idea of what damping factor is all about.
If you haven't already, look through the various audio forums and see what other people are using with their maggies or post a question looking for the same information. Also include some information on the "sound" you are trying to achieve as well as your budget.
Finally, if you have (a) good local dealer(s) then talk to them. A good dealer should be able to help guide you in the right direction and most will also allow you to borrow equipment to try in your system. If your dealer provides this service and helps you out it would be wise to return the favor and buy whatever component you decide on from that dealer.... otherwise you may find that the good advice and loaner gear made unavailable to you in the future.