Unless your brain works algebraically, and not in Reverse Polish Notation. I find that most people adapt to the 17 B II more quickly than to the 12 c. But if you are a purist, you can run the 17 B in a RPN mode.
I prefer the HP 17 B II. In fact, I have not been without one ( I'm on my second, first one finally gave up the ghost after 10 years) for 16 years.
The 17 B II has a program function, where you can input your own equations, and will do cash flow calculations, Present value calculations, and statistics/Math calculator functions.
The users manual that comes with the calculator has some of the best cash flow and time value of money explanations I have ever read... and I am definitely a finance weenie.