I've been a freelance writer for a few years (but only found this forum as of today, ta da!) and in my experience writing essays for people is more lucrative than articles for companies. I did the latter for a long time before I did the former, so I have some experience with both.

The thing with writing articles for companies is that it's much cheaper to farm the work out to individuals in places like India. Most companies that buy articles do so for marketing purposes, and they don't need to meet the same quality standards a piece of academic research or an essay would.

Hope that helps some!

Alexander