Calculators Ti89 or hp50 or what? Need help

ti89 or hp50 or what? Need help!!

hi. I'm an econ student and taking courses like international economy, monetary econ, and econometry. in econometry we use statistical formulas and such. and lesson is full with formulas and some of them are long (including derivatives). I need an advice. I m looking for a calculator that I can store loads of formulas even proofs (long long formulas). So it needs to show formula with details. I dont know what to choose. It doesnt need to be graphical but if my needings exists on a graphical one I will choose no problem. As far as I saw that graphical calculators have huge screens that can store long formulas. So waiting for an advice I dont have a money limit just need to choose best one. I just noticed ti89 titanium and hp50g so need serious advice it doesn't need to be one of these. just waiting advice...

 

yes but I said my needings so just need an advice. no limit for budget as far as if it supports my needings as I told in the main post