A new type of list in which journals who applied for SCIE gets listed initially while the evaluation is going on. And journals of local importance also gets included in this list. But there is no indexing of papers in Thomson Reuters and also no impact factor is calculated for such journals.
So paper accepted for an ESCI listed journal is a good thing but not as good as in SCIE. Yes It is helpful.
Journals indexed in the ESCI will not receive Impact Factors; however, the citations from the ESCI will now be included in the citation counts for the Journal Citation Reports, therefore contributing to the Impact Factors of other journals. If your journal is indexed in the ESCI it will be discoverable via the Web of Science with an identical indexing process to any other indexed journal, with full citation counts, author information and other enrichment.
The Emerging Sources Citation Index is a citation index produced since 2015 by Thomson Reuters, and now by Clarivate Analytics. According to the publisher, the index includes "peer-reviewed publications of regional importance and in emerging scientific fields".[1] It has been observed that among the databases produced by Clarivate Analytics, the Emerging Sources Citation Index is the easiest one to get into and that as a result it contains many predatory journals.
Together with Science Citation Index Expanded, Social Sciences Citation Index, and Arts and Humanities Citation Index, the Emerging Sources Citation Index is accessible through the Web of Science.
SCI is of better quality than ESCI as journals of SCI are included in the impact factor/JCR list. ESCI is an indexing mainly comprising of emerging journals but it is also of good quality and many countries and universities recognise it
Emerging Sources Citation Index is a new edition in Web of Science Core Collection. ESCI is a multidisciplinary Citation Index covering all areas of the scholarly literature of the sciences, social sciences and arts & humanities. The Core Collection Journal Selection Process now includes a set of fundamental criteria that govern the selection of Journals for ESCI. The selection process for ESCI is related to the process applied to SCIE, SSCI and AHCI. Journals accepted for coverage in ESCI must be peer reviewed, follow ethical publishing practices, meet our technical requirements, have English language bibliographic information, and be recommended or requested by a scholarly audience of Web of Science users. While some journals under evaluation are selected directly into one or more of the äagship Citation Indexes (SCIE, SSCI, AHCI) many other eligible journals will be covered initially in ESCI. Journals covered initially in ESCI may be evaluated later for coverage in SCIE, SSCI or AHCI. Coverage in ESCI, however, does not guarantee eventual acceptance into SCIE, SSCI or AHCI. Indeed, some journals that need to be deselected from coverage in SCIE, SSCI or AHCI may migrate to coverage in ESCI. It is important to note here that coverage of journals included in ESCI is never duplicated in SCIE, SSCI or AHCI. Coverage in ESCI is entirely separate from coverage in one or more of the Core Collection äagship indexes (SCIE, SSCI, AHCI)
Emerging Sources Citation Index (ESCI) journals do not have impact factor. Therefore, we can’t say ESCI journals quality are not good, but not good as Science Citation Index (SCI) and Science Citation Index Expanded (SCIE) journals.
So, the first priority should be given to SCI and SCIE journals to publish a scientific article.
Journals indexed in the ESCI will not receive Impact Factors; however, the citations from the ESCI will now be included in the citation counts for the Journal Citation Reports, therefore contributing to the Impact Factors of other journals.
If your journal is indexed in the ESCI it will be discoverable via the Web of Science with an identical indexing process to any other indexed journal, with full citation counts, author information and other enrichment. Articles in ESCI indexed journals will be included in an author’s H-Index calculation, and also any analysis conducted on Web of Science data or related products such as InCites.
Indexing in the ESCI will improve the visibility of a journal, provides a mark of quality and is good for authors. Many institutions and funders are suggesting publication in an ESCI listed journal, similar to what already takes places with other Web of Science databases.
For the second part of the question, it is definitely worth to publish PhD works in ESCI journals.