Yes, for any equation you have to mentally perform the infix to postfix notation conversion. And where the calculator can do this quickly, the algebraic I notation calculator will have the lead.
Any calculator using algebraic notation must do the conversion to RPN (or similar) in code (even if they do it very badly). This requires memory and processor cycles that the early calculators did not have in abundance. I remember some AOS calculators literally taking seconds to display a result.
HP eventually switched to AOS for student models because to do otherwise would be to be making a significantly different thing that teachers would have to allow for. At the same time, galloping featuritis pretty much killed the handheld calculator as it tried to emulate a computer or be all things to all people.
I taught my wife to use an HP-28 (AOS) while I still used my HP-41 or occasionally an HP-21 at work. (As she pointed out, what use is a calculator collection of she couldn't use any of them)
It is also interesting to note that the HP calculators seem to have survived the decades far better than the TI models. And that's a shame because they were pretty much fierce competitors at the time, forcing all sorts of technology into the hands of people like myself. It is interesting to note that for a long time the Space Shuttle carried HP-41's along for a number of purposes including very basic deorbit burn calculations.
http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/archv001.cgi?read=2577