It’s for an internship, so it’s not life and death if it does not work out.
If you want criteria not dependent on what you want to do, then consider what I already said above:
- What are the chances of converting to full time offer at the end of internship
- Do you mind longer hours – I imagine Google would be slightly more leisurely, though technology at a bank isn’t that intense either.
Ideally for most of these try to Google evidence up, as especially a bank will tell you all kinds of sweet stories BEFORE you are in.
Otherwise, you can’t decide this just by reading peoples posts on this forum. Ideally get hold of someone working at each of the places (i.e. not HR, but e.g. for Goldman’s someone from the team you would be working in) and ask concrete questions like “What did your yesterday look like?”, whatever, to get a feel of what you would actually be doing. However, ask neutral information questions, i.e. not stuff like “Do you enjoy this”, etc.
Also, re your PS – unfortunately, it’s extremely unlikely that you could do that, but not impossible. Most banks have front and back office strictly separated (with middle office appropriately somewhere inbetween those 2) and back office has typically truckloads of people who want to be in front office, e.g. sales or trading. 99% of the time this does not materialize.
If you would want to do trading, you would have to start working on that goal right now. But given you don’t have a clear view of what you want to do, if you do decide to go that way, you have to do massive investigation if it’s right for you. It would be a career choice, so whatever you decide, don’t just sit there and write on forums, try to gather up as much concrete evidence as you can to support your decision.
Hope that helps.