UCL or QMUL? Watch
In terms of your experience and how much you'll enjoy the experience, rankings aren't a great measure, but when it comes to someone looking at your CV, you are in a much better position if they see UCL than if they see QMUL. This is called signalling, as in going to UCL will send a stronger signal that you are smart and employable than going to QMUL.
Making decisions on this basis is, I grant, a bit f****d up at the societal level, but there's nothing we can do about that.