Anecdote, but I was surprised to find that my father (who used his HP with RPN extensively) found "normal" calculators more difficult to use. At the end of the

Anecdote, but I was surprised to find that my father (who used his HP with RPN extensively) found "normal" calculators more difficult to use. At the end of the day I think it comes down to what you're used to. Requiring more or less mental activity can come down to how closely the activity matches what one is comfortable with.