Does anyone have any direct experience. DS will do it and his school advises it gives university applicants an edge. DD's school has said they won't consider it because they don't think the uni's are unduly impressed. DS would like to read classics or english at Oxbridge.
My daughter is in her final year. We're not in the UK but here the IB is definately seen as more favourable and IB courses are the most over-subscribed as a result. They get to pick and choose who they take. For exceptional students, I think there is more room to impress with the IB. I've had a look at the Oxford classics website. They require 3 As for A-levels and 38-40 points for IB see here. The maximum available for IB is 45 points see here. Although getting the max is rather unusual (here anyway).
My DD has just finished her IB, (38points) and we would recommend it to any able student, especially if they are uncertain of their choice of study at uni. It is more demanding academically than A levels, has a much broader curriculum and is very well thought of by universities. All candidates at my daughters school received good offers and she herself got all her choices. Would question your Dd school's reasons as ALL Russell Group unis love the IB.
disadvantage is that universities don't always appreciate how difficult IB is compared to A levels so offers for IB tend to be harder to achieve than the corresponding A level offers for the same course. I know one or two children who missed their IB offers who are convinced they would have easily met the A level ones had they done A levels (though I conceed there may be an element of the grass on the other side always seeming greener here).