Both calculators are currently allowed on the SAT (but neither is allowed on the ACT because of the CAS-computer algebra system). The TI-89 titanium doesn't have inbuilt stats but it is an easy download of the ti website. other than that it has all functions you need (calc, polynomial, summs, programmablity, 3d graphing, etc). From what i've heard ti nspire cas is very similar in functionality with some extra bells and whistles (and i think inbuilt stats) and a bigger screen, processor, etc with a little better connectivity to other devices, but as far as math goes the titanium is more than complete.