more pages or more sites

I would say that as a rule its good to concentrate efforts on one potentially strong site. Nevertheless, creating a network of support sites might give birth to another 2 strong or semi strong sites. I've noticed that once a site starts to rise in ranking (as a result of some added content or good links work) than adding more relevant content, regularly, helps maintaining high ranking and even pushes the site even more. This is true about Google. Bing, Yahoo and some others seem to be able to put your site as #1 even with 1 page and 3 inlinks.
My best recommendation is to load a site with at least 5 pages to start with. If you have a good idea for a kw which is a bit far of your main sites kw's. Just create another site which focuses on that new kw or long tail.
The added value of a network with all authority levels in it makes wonders.

I think as affiliates we always start out as one man bands. Everything is our own idea and we take responsibility for every decision.

2-3 years later that one man band situation can be the only thing holding your business back.

I think the key to being able to launch more sites without just diluting efforts is to outsource.

But then there's good outsourcing and bad outsourcing. Once you have a good team working for you, you can launch 5 new sites without diluting anything.

I always look at it by comparing the independent corner shop owner to Tesco. Seems like a silly comparison but there are some real lessons when you think about how they each operate.