Which way to go...

Which path would be better in the long run? Should I work as a Business Analyst in a bank such as JPM (back office) and then try to work my way into other areas in the bank such as risk management etc? or should I just look for positions such as, Junior Analyst in small asset management firms and move onto bigger things from there? Is it easy to move from one role (more IT, back office) to another (more finance) in bigger orgs such as JPM, Lehman?