Landed an internship in a BB, two weeks after joining a local IB boutique

Hey guys,

Bit complicated situation here. In short, I've recently started working as an off-cycle intern at a local IB boutique in my country (it is unarguably the best local boutique, but my country is pretty much unknown in global terms).

However, today I received a call in which I was offered a 6-month IB internship at a BB, after a very long interviewing process. Both internships offer me the possibility to convert it to a full-time position. 

I want to take the internship at a BB, as one of my goals is to move to a global financial centre (NY, LDN, HK, etc) in the future. However, I am aware that leaving my current job two weeks after having started working would likely burn bridges.

I would really appreciate any advice on how to handle this situation, as I feel this decision may be seen as unethical or unprofessional

Thanks in advance,