From what I could tell when I was looking at schools, the IB is recognized more, since it is also used in the States. Many better schools require that you obtain the IB diploma (or whatever it is, I did AP's because that's what my school offered) to be able to count anything off your degree.
Then again, most expensive, nice, high-level private schools don't let you skip any classes anyway - public universities sure, private not so much. Personally I took about 9 AP tests, passed 7 of them with 4s or 5s, and I got an elective credit for one history (I still have to take a required history class, too), and got to skip the easy English class for a harder one, without getting any credit. At a UC, I would have been going in about Sophomore level. That's just how it is. Most Ivies are about as strict as my school.
I also will say that I know someone from my school who did a full IB program and they got about 3 classes out of the way that way. It really just depends on the school and what you end up actually taking.