@kyle it looks like is the easiest mechanic calculator to operate. The other seems more like hard core devices.
@Konqi It has the advantage of an electric motor to take the place of levers and cranks. It also seems easier because the UI is closer to modern calculators we are more familiar with, which makes sense, since electronic calculators started coming out a bit over a decade later.
@kyle @Konqi even on modern calculators just about everyone expects algebraic notation, so if I give someone my HP there is a near zero percent chance they can even add 2 + 2 since it uses RPN. The flipside of this coin is of course that after heavily using RPN for years I can barely use a regular calculator myself.