Hello. First ever post, so excuse me if I waver from standard chat routines. I teach IB diploma and A Level too. IB is excellent and A Levels can be too.
There's an important point that not all subjects equate directly to their A Level counterpart. For example many A Levels A grades are roughly a 7, but Higher Maths is for serious mathematicians only. In other subjects, a 7 might even be easier than an A.
The IB is hard work, but so is life. It may be easier to get into some courses at some universities with A Levels, but not all. The pattern varies within subjects and univerisities and is often oversimplified. For example, it's very hard to get into Maths at Cambridge with IB, as they want Maths and Further Maths and aren't really interested in anything else. But Maths at Oxford is arguably easier to get into with IB than A Levels.
You absolutely need to get the blinkers on and consider your child's needs and strengths, rather than anything else. If they are not all rounders and are fixed on a career in a field such as Engineering, then A Levels are right for them.
An important thing to consider is that A Level students apply with AS scores, rather than school-based predictions for IB students. This means that A Level students need to be on the ball immediately and cannot afford to slip up, whereas IB students could still get a high prediction to apply with even if they haven't excelled in the Lower Sixth, as the teacher can use their discretion and knowledge of the student to form their prediction. Anything less than all A's at AS at the same stage can close the door on many top universities. There is a myth that A Levels are easier, but I'm not so sure. IB may be more work, but not always harder work.
I had a student who missed their offer and insurance with 32 points, which is a modest score. They got their results at the beginning of July and were able to ring around and secure a Russell Group place in a very competitive subject before the A Level results were even out.
Just a few thoughts, sorry they are slightly rambling. IB and A Level are both strong and most able candidates will rise to the top either way.