You need to think about why you want the qualification.
- Do you want it as a pre-requisite for entry into an educational establishment?
- Do you want it in order to get professional work?
- Do you just like collecting qualifications?
In all of these cases, I honestly believe the qualifications are pretty much equivalent. There aren't colleges or employers who would accept one qualification, but not the other. You might yourself think of one as having more prestige than the other - but that's a gut-feel Pepsi/Coke distinction that only you can evaluate.
However, don't take my word for it. Ask the employers and colleges that you're interested in what qualifications they look for.
Alternatively, you might not care for the certificate at the end, only being interested in the actual skills you learn in getting there. In that case you need to look at each syllabus in detail (they should be openly available), and see which one involves learning the skills you want to develop.
One big factor, is your teacher -- assuming you are using one. Your teacher may well have a preferred qualification, for which they know the syllabus, and with which they have experience teaching.