I am going to guess that both will be adequate prep for calculus. IB SL includes some calc, some stats – more of a survey of math topics. The other route will take you to calc’s doorstep. I would say that if you aren’t going to take calculus in high school, pick the one with the best teaching.
Is there any way you could do the 2 year math SL track so that you would have calculus in high school?