Recently, I presented a talk at a conference and am considering writing up the paper for the conference proceedings. However, I also thought that it might be nice to submit our research to a journal so as to reach a wider audience. The two questions that have arisen are:

1) Can one submit to a journal a paper that has the same or similar content as one that is being submitted as a conference proceeding? 

2) What are the relative career merits of publishing in a proceedings or a journal?