All types of engineer played their own part. U maybe a civil or mechanical or electrical or chemical or others.. but somehow all these engineers will come across each other in the end. that's y engineers alwiz work together. but if you are the leader of a certain project, u maybe need to know or have a little bit of knowledge about everything. For example, you are a mechanical engineer but u dunno any chemical process or electrical things, u will have to absorbed some of their knowledge in order for you to be successful in your project.
Normally, IR will become the head of project or a consultant of a certain project. If u are interested to be one then IR should be your choice. There are others who will try to get the title just to prove to themselves, they are engineers. To me, IR is just a title like 'Tan Sri' in the royal title.. haha.. u may not earn as much money with a same engineer without an IR title in the end. So, its your choice, and yes with IR u will have a better future no doubt about it, cause when u are on the road to get the title, the path is not that easy.. ur experience counts too..! =)