How to balance summer offer and full-time offer

Hi everyone,

I have fortunately received some summer/off-cycle offers and recently a full-time one in this cycle.

The issue is that I received an off-cycle (basically summer since start date is in June, ends in Sep) offer from a European BB back in November, which I signed.

However, I still continued to interview for full-time analyst positions and received an offer a few days ago for a trading position at an American BB. Naturally I prefer this offer (it is in a similar area to what I was doing before), and I assumed that I would start in Sep. However, the graduate program involves going to NYC for training in early July.

In such a stuation should I:

a) Ask for a later start date from the American BB such that I can honour 8/9 weeks of my internship contract at the European BB (I assume NYC training is more valid for contact-building with other analysts rather than technical training - since in my case I have studied Quant Finance and have European (not UK) trading licences (Eurex/Xetra/IDEM)).

b) Let the European BB know of my full-time offer and mention that despite me signing their contract, it is not worth me joining them for an internship if I am going to be moving to another firm on a permanent basis immediately after the internship completion. That way I can be in NYC for July for the training with the American BB.

I am leaning more towards option b) since I think banks would expect you pursue an internship with the intention of gaining full-time employment at that firm (rather than elsewhere). Also, requesting the American BB to wait for me (for 2 months) just so I can intern at another BB probably won't look good.

Do you agree that b) is the option to go with here (despite my signature of the intern contract back in Nov)? BTW, the offers are in different areas (FICC vs EQD) so I'm not moving to a direct rival desk.

What arre your thoughts? Thanks in advance :)