Impact factor or SJR?
There are several types of journal/citation metrics that are available at our disposal to evaluate a journal. These metrics are often a deciding factor while considering grant applciations, fellowship applications, job applications etc. The Impact factor was one of the first journal metrics that is still widely used. However, a widespread misconception amongst researchers is that the Impact Factor is used to measure the quality of a journal. In reality, the impact factor of a journal has nothing to do with factors such as the peer review process or the quality of content that is published in it, rather, it is a measure of the quantity of average citations that the articles in a journal receive from other journal articles, books etc. It could also be used as a measure of the relative importance of a journal compared to other journals in its field. The impact factor of a journal for a given year is calculated by measuring the average number of citations per article that was published in that journal in the previous two years. For example, an impact factor of 5 in 2018, would mean that the papers papers published in 2016 and 2017 received 5 citations each in 2018. Therefore, as you can see, this metric in any way does not measure the quality of a journal.
The SCImago Journal Rank (SJR Indicator), also does not measure the quality of a journal, but is a more holistic approach towards comparing the relative importance of journals in any given field of study. It is a measure of citations received from a journal as well as the importance or the prestige of the journal where these citations come from. SJR can also sometimes have drawbacks such as gaps in the coverage of journals and errors in assigning published documents in Scopus.
The basis of citation metrics is essentially the assumption that if a piece of work is cited by another researcher, then the research is impactful. There are several other metrics such as the Eigenfactor, Source Normalized Impact Factor (SNIP), 5 year Impact Factor etc. that come with their own set of pros and cons. Therefore, it is difficult to say which one is better than the other and it is best left to the judgement of the user to decide which one of these suits them the best.
In order to understand and evaluate journal metrics better, you can go through our course titled Understanding Research Metrics: Impact Factor, Altmetrics, and H-index on Enago Learn– Our Comprehensive e-learning platform.