The HP10bII+ is a different animal from the different versions of HP10bII. It is a far more complete unit, having lots of scientific functions in addition to the whole HP10bII lot, and several additional financial functions too.
Among the scientific functions:
And then you have the full list of financial functions: cashflow, IRR, NPV, depreciations, bonds, Time Value of Money, and breakeven calculations (this is also a first for this function). All in all, a very complete calculator. Let's not compare it for a moment with the original HP10bII - which was a quite simple calculator in comparison with this one.