Hey guys,

I want to pick up a CAS graphing calculator used, and I can't decide which one to get.

I'm leaning towards the Nspire CAS because I already have a TI-Nspire CX (non-CAS) that I use for school and other standardized tests, but I want CAS for Calculus and to write my SATs. That allows me to basically copy over my files and custom functions I've programmed into my CX, but then the TI-89 has better apps...

With that being said, I might as well just buy both...

I have both. I kinda hate the nspire's document system. The onboard BASIC functionality suffers because of it. If you're really serious on programming the nspire you will have to go the lua way and do it off calc.
But then there is a lot to like. Color screen, high resolution, amazing speed. It's a fancy calc while the 89 definitely shows its age. Since you already have the non CAS model I guess it is a no brainer.

I'm selling my TI-nspire CAS for $40!
I would recommend the TI-89 for programming, and the TI-nspire for maths.