For me journal paper deserves intellectual justification of some body and conference paper is simply a social exposure. Journal publication has high value in academic setting in comparison with conference paper.
Journal publication! For promotion purposes, some publications are worth 15-20 points whereas a conference paper is worth 1-2 points! A paper sent to a reputable journal is reviewed by at least 2 experts, whereas the participants in the conferences (I have attended) generally listen to you and put their hands together at the end without giving you any thought-provoking feedback. However, it also depends on the conference! Presenting papers at symposiums could be useful because they normally focus on one area only.
In my opinion, publishing a research paper in an ISI-indexed journal is better than in the conference proceedings (even reputed conferences such as IEEE, ACM conferences).
In a simple way, both of them are type of publication and you can choose one of them based on your aim in specific time and condition. Proof of this, the most of researchers in this website are publishing in journal and conferences.
Each one has its own merit. Conference proceedings will help you to interact with several scientists of your field. Here reviewing procedures is not not rigours. Peer reviewed journals have rigorous reviewing and are usually experts in the topics. Hence more credit is being given for assessing your work.
Which is better, a journal publication or conference paper?
Advantages of publishing paper in conference:
Content of the conference paper can be shorter & focus on specific topic - generally easier & faster to write (vs journal article).
Can share the latest research outcome faster from writing to publishing in conference proceeding.
Conference paper can be an instrument to tell the world / research community you are embarking / working / completing the research in specific area so that other researchers not "re-inventing the wheel".
Publishing paper in conference also include presentation to audience & follow by Q&A - this can help crystalize the audience's understanding & generation of new ideas / improvement for the presenter (author of the conference paper).
Through conference, the presenter can interact / socialize / network with other researchers in the similar field for further brainstorming / collaboration.
Advantages of publishing article in journal
Mainstream deliverables to improve the academic status of the author / gain recognition from the university or research community (especially publishing in high impact factor journals).
Higher quality of published work after gone through more stringent blind / peer review.
Can improve the author's article writing skill after gone through rigorous stringent requirement from blind / peer review e.g. what need / need not include in literature reviews, choice of words used, justification of points posited etc.