Been there, done that. Here's my thoughts.
HP 10BII - Not enough functions. Stay away from it.
HP 12C Platinum - Good functionality but not user-friendly. Ancient interface. Only good if you are an old pro at it and are used to the way it works.
HP 17BII+ - Lots of functions and easy to use. Menu-driven interface. Overall, it's my favorite financial calculator, even though the quality is not as high as the old HP's. Because it has memory and solver functions, it can be considered a cheater's calculator. Some professors might not allow it.
TI BA II Plus - Best value. Lots of functions for both finance and statistics. I found it easier to use than the 12C but more difficult than the 17BII+. Does not have memory or solver functions, so you can't cheat with it, but it's always allowed on tests. If you can only have one calculator for your MBA, this is it, but I'd rather have more than one.
PDA Calculator - My favorite is the CRE Calculator from Infinity Softworks (
www.infinitysw.com). It is not an emulator. It is specifically designed for PDA's. Very easy to use and lots of functions, but many professors won't let you use a PDA for tests.
My overall suggestion is, if the professor allows it, bring the CRE Calculator to your test. You'll get through the test faster, and you won't have to worry about messing up because you forgot how to use your calculator (which can happen under stress). If you can't use a PDA, use the HP17BII+. In any case, always have the TIBAII+ ready as a backup in case the battery on your primary calculator runs out or the professor does not allow anything better.