Actually, it depends upon your purpose. If you want to setup a blog and your means of monetization is Adsense, write blog posts or articles that has a high number of searches, high CPC and competition bar is full or almost full (this would ensure that a lot of advertisers are bidding for your keywords).
Having a full bar on competition bar will not result to low number of pages on google so your number 4 is the opposite result on clicking on the keyword in adwords result if the competition bar is high.
However, if you plan to be the first in ranking with google if you want your blog to be seen in google search on the first page, this would be achievable if the number of pages is low, but you have to balance this if you want also to target more advertisers bidding on your keywords if you monetize with Adsense.
Check out my blog on this ---> http://hubpages.com/business/google-adwords-resear...