IMO,
Articles have a great title normally written around keywords and submit to the appropriate directories. It is time intensive if done manually or you can acquire an article writing software and an article submission software to make your job a lot easier.
A blog has a similar format. You have a keyword title, good to great writing and it is a bit more intimate and conversational. If you set one up, be sure to pay for hosting. You can build one for free but if you want to be taken seriously get one besides blogger.
Press releases, as far as I know, are either written for free or for fee, have a similar format to articles and blogs and should be done as professionally as possible with high visibility upon the launch of a product or service.
The press release introduces your blog which is promoting your service or product and your articles drive traffic so that you create revenue. Keywords are of the utmost importance.
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