ESE

The Indian Railways will now recruit officers through the IRMS exam, and only the prelim stage will be common to the UPSC CSE; the other two stages have separate exam structures. Both ways are good; if you want to join for generalist positions through IRMS, CSE is better, whereas if you want to become a specialist, ESE is better.
1. Salary: Both services are group "A" services with an equal salary structure as per the seventh pay commission.
2. Nature of work: The IRMS's work is to look after management in the railways, whereas ESE includes branch-specific work such as mechanical engineers in the railways, who will work in the Mechanical Engineering Division of the Indian Railways.
3. Exam: Through CSE, you will be required to appear in the common preliminary. The CSE prelim syllabus is significantly larger than the ESE prelim syllabus. The questions in CSE are more general than those in ESE, which will be more technical in nature. In addition, unlike ESE, which is branch specific, you can select your optional for IRMS in main.
4. Career advancement: The promotional scale is similar, but you will have more diverse work opportunities in IRMS, unlike ESE.

For Junior Telecom Officer Group-B, you will have to undergo 6-7 months of training at the National Telecommunications Institute for Policy Research, Innovation & Training (NTIPRIT), Ghaziabad (including 2 months of attachment with Department of Telecommunications, Telecommunication Engineering Centre, and Licensed Service Areas). After successful completion of training, you will be posted as a JTO (basic pay INR 44900 per month, level 7) at field units of the Department of Telecommunications. After completing 2 years of regular service as JTO, you will be eligible for promotion to the next grade which is Assistant Director, and the basic pay is INR 47600, level 8. After completing 3 years of regular service in level 8 as Assistant Director, you will be eligible for promotion to ITS Group-A, I. e. level 10 job. So, at least 4 years to get a promotion from JTO Group-B to ITS Group-A. I hope this will help you.