DS1 did the IB and when it came to DS2 choosing, DS1 was shouting "Do A levels" from the rooftops. According to him, those doing the IB had to work much harder than those doing A levels, simply based on the amount of subjects they were doing. This was just his observation of course. The following are my musings and observations - I'm not pro/anti one or the other.
People talk about leaving your options open by taking the IB but in reality you can only study something at university that you have done at higher level and not standard level so what does doing these standard levels achieve with regard to entrance to university (what they achieve on another level is obviously different)?
Some of the higher level subjects are more difficult than A level. Higher French for example is certainly more difficult than A level French. I'm a maths tutor and I would also say that higher maths is more difficult than A level as there are elements of further maths in there.
There is a UCAS IB tariff here but it doesn't seem to be applied very much at any point in the university scale. At the lower end, to be fair, they are unable to use the tariff because a course which requires 160 points will have to ask for 24 IB points as this is the minimum pass mark but this, according to UCAS is 260 points. Mid-range, 34 points equates to four As but this comes, for example, from the University of Kent website for admission to their maths course:
Offer levels
A/AS level 300 points (3.5 A level equivalents) inc BB at A level, IB Diploma 33 points inc 5 in HL Mathematics or IB Diploma with 15 points at Higher inc 5 in HL Mathematics, except for Mathematics inc a Foundation Year (G108) (individual consideration).
So basically they are asking for three Bs at A level (two Bs/300 points) whereas 33 points equates to 3 As and a B.
At the top end, 45 points (amazing if you get this - the highest in DS1's year was 44 and that was already considered amazing) equates to 3 As and 3 Bs (or 6 As). To study French at Cambridge you need (in theory) AAA, so 380 points. For the IB, This is what it says:
Typical offers are 39-42 points out of 45, including 7,7,6 or 7,7,7 in Higher Level subjects.
For a start getting three 7s or even 7, 7, 6 at higher level would be harder than getting A*AA, without the overall requirement to get 39 points which is, according to the tariff, worth 589 points (42 IB points = 654 UCAS points).
I thought that Cambridge would be one university where they would like the IB, given that it distinguishes more between top candidates but they are asking for exceptionally high grades. I realise that those going there with A levels are likely to have higher grades than they are asking for, but I am only looking at what they require as a minimum according to their website.
I think I would advise the following. If your ds has a idea of what he would like to study, do a bit of research with the universities offering that course. Draw up a table of the IB versus A level requirements, including whether they ask for specific points in higher subjects (as they usually do). Then weigh up whether or not you think it is worth him keeping up the three standard subjects (from the point of view of getting into university) which in reality won't specifically help him get a place on a course.
Also take into consideration maybe the fact that with the IB there is the compulsory Theory of Knowledge element which whilst adding to your points also adds to the workload.
On the plus side, having to work for so many subjects will, I believe, make him more prepared for the amount of work he is likely to be expected to do at university.
Hope this helps a bit!