I was asking myself this question today: Does enabling the content network for a campaign affect the performance of your normal search targetted ads? I see my campaigns average ctr drop dramatically, but at the same time i'm starting to doubt this matters in any way. This doesn't affect the quality score of my keywords right? The CTR rate for my ad group also drops dramatically because of the thousands of views and hardly any clicks. Would there be any point to split a campaign in two, having one for the search targeted and another identical campaign for the content network? what is the main reason most articles contain the advice to disable the content network when starting with adwords? because it is to much to start with everything at the same time or are these ads generally more expensive than search ads?
Having split campaigns is a good idea. It will make it easier to keep accurate track records of performance of the content vs. search network ... and it should also help answer your questions of which cost more, plus you can evaluate the ROI and decide whether to go with either or both.
No, content activity doesn't affect search activity. Look at the bottom of any of your ad groups on the keyword tab: "Lower CTRs for content ads do not adversely affect your campaign." People tend to create seperate content campaigns because the content network is a different animal and requires a different approach (at minimum ad copy) to be successful.
I usually prefer to split them into different campaigns for better control and tuning. Just like Guyfromchicago said, they are different animals