Clinical Operation would have better option if you are looking for long term goal. Though i am not saying that CDM, PV and Medical Writing are not good these are also equally good.

But in Clinical Operation- You will have broad area to develop from CRA to Monitoring Lead to Project Management, Program Management and Portfolio Management. Once you will start working for big CRO or multinational Sponsor then you will get to know more on this managerial skills.

And if you will work in Project Management domain then CDM, Medical Writing will come under PM as well. and You can have overview of whole clinical trial process.

So I recommend CRA (It comes under Clinical Operation)would be better option in initial career. You should except some challenges in CRA role like frequent travelling and stressful journey but once you gone through this you will see rewards very soon. and then you must develop your management skills to grow in your field.