most analytical role in the market need a master and it is better for further development in long-run
it is better to study that earlier than later (before you forget everything and lose the mood of study, unless you are planning to read that part-time later), and thus I will strong suggest do it first....
indeed you have many choice:
1. business analytics: get some business sense and networking, and how people apply data analysis in business.
2. financial engineering: get a bit more on the stochastic modelling side, and fight for a risk role.
3. economics: more economics theory is very useful for further research in economics and finance. useful for roles in central bank and policy unit (well these are not for international most likely.....)
4. computer science: if you want to go for a developer role, more experience in coding, some more idea about algorithm, are all good preparation for data scientist and or data mining stuffs.
5. statistics: given you have a bachelor already (i.e. I guess you had read all those multivariate, time series and inference stuffs), the only useful statistics master to you are those really mathematical (and theoretical) one. They are very useful if you want to read a PhD in Statistics or Econometrics.
6. and etc......