The chase after attention is an indispensable part of scientific progress. When paying attention to the research done by others, those demanding scientific information are, in a manner of speaking, collaborating with those providing it. This team-oriented, altruistic aspect of science (that aims to save everyone a little time and effort) is one of the main reasons why scientific congresses and journals make sense. However, which of these two venues is more appropriate to publish your work?
Why to choose journals: Journals are quite convenient for scientists who are just starting their careers, as they have higher acceptance rates. Another reason to prefer journals is that they give you the opportunity to include as many experimental results as you wish, information that otherwise you might not be able to fit in a conference publication. In a journal you can also add extra proofs that are too long for a conference talk.
Reviews are another key point to take into account. While conference reviewers usually believe the researchers’ assertions, journal reviewers are supposed to verify them. That’s why journal reviewers might spend a lot of time on a paper whereas conference reviewers simply cannot afford to do so. Considering this your preference should be for journal publication because a detailed revision can help you to improve your work (or to understand its weaknesses) before you re-submit it.
Why to choose congresses: The most obvious reason why you should publish your work in a scientific congress is that conferences provide higher visibility. Researchers in the same discipline will attend the talk, ask questions and, most important, will become aware of the innovative research being generated in your particular subfield. Receiving feedback from peers may also help you to eventually write down your study. Moreover, you can establish contacts for future employment and you can also learn of available positions sooner than anyone.
Journals (even the best) are less selective than congresses. The rush for some researchers to send even marginal results tends to lower the overall quality of journals, while congresses usually have higher quality.
In short, regardless of which venue you choose to publish your work, the primer motive of journals and conferences is again the same: make you and your work visible. And, of course, practice your writing and your presentation skills!