^ Well, to back your statement, Solya, we can look at percentages of students receiving specific grades.
My sister was rejected from Imperial because she achieved 37 points while her offer was 38. However, she got a 6 and 7 in higher chemistry and bio, and a 7 in maths (not HL). The percentage of students who received a 7 in Bio this year was 4%, as opposed to something like 33% getting an A at A level. If she took A levels in bio, chemistry and maths, I can almost guarantee you that she would have achieved 3 As, but sadly her other subjects in IB brought her overall score down. She applied for biomedical science, just to make that clear.
Less than 10% get 7s in Higher subjects at IB, as opposed to A level, where about 30% get As in the sciences, 40% get As in Maths (and even 50% in further maths). There's gotta be some sort of Discrimination against the IB!
Now I'm no expert on A levels, and I don't disrespect anyone taking the A levels, but looking purely at percentages (and considering that in general, the IB is more available to upper class people - who are expected to score higher), there are potential students who take the IB getting rejected from universities that they deserve to get into.
If you want to switch to A levels, and you feel that the IB isn't for you, I suggest you go for it...