A PhD programme is a long term project. On an average, it takes people about six years to complete their PhD. Before actually venturing into a project of this stature, it is a wise thought to stop for a moment and think of your plans after a PhD. A lot of scholars get into the field of academics and some follow the route of research.
If your choice is to work at the university, there will be a certain set of responsibilities that you would be an integral part of your life. You would have to working with students, teaching in classrooms, working on grants for your college or university, doing other services for your department. In this scenario your life revolves around your job and it may work very well for some people and equally unsuitable for some of them. I you specifically want to work for a research university, your work may give you the divided attention towards doing research on the topics of your interest and expertise.
However, if your preference is not teaching and a lot of regular interaction with students you have the option of another very interesting work profile. It is more challenging as every time it may give you unpredictable challenges to work upon and newer and more topical research areas to focus on. Your key schedule in the case of working in a research lab would be, partially to undertaker research on what you want to, at your discretion and partially, on the topics and areas specified by the company you are working for and who their clients are. You may have to work with others in the company slightly more with as compared to being a professor at the university. This job may involve some travel and working with others as it is away from teaching and more in the arena of a corporate set up.
Of course, after completing PhD you may choose to work independently as a freelance consultant for research firms and universities. That would give you more freedom and space to schedule your research and tasks as per your liking and without much bounding and constraints