WP MU (wordpress multisite) or separate WP sites?

So I have a client that has a newspaper. Im pushing him towards WP with Magazine theme.

Now I have to decide what is better for him Multisite or separte WP installations on subdomains?

He only has one domain name but puts out different editions for suburbs.

Say his site is whatevernews.com

I`ll create the subdomains city1.whatevernews.com,city2.whatevernews.com,city3.whatevernews.com etc. etc.

What would be the benefit of doing this as apposed to separate WP installations on each subdomain?

With Multisite, you can control all the plugins from one place. You can also access any page in a click. With regular WP installs, you'd have to login to each one to edit it.

Multisite is awesome when it's setup, just get a multisite plugin, and it will be installed in 30 seconds.

One thing I am concerned about is the articles he posts on one site should not be on another site.

So the articles posted to city1.whatevernews.com should not be viewable on city2.whatevernews.com

How do you mean MU plugin?

Its a good thing to be concerned about the duplicate content issue. Google will definitely see it and most probably penalize the site by dropping the site in the rankings.