Would you humor me with an example of what you mean by "thinking on the
fly"? Either I'm not understanding you or we think differently.
I'll take a stab at it in a minute.
But first, I never cared either way. In college, I had an SR50 and my GF had an HP45. I would say, between my EE friends we were probably split 50/50 between TI and HP. Generally, it was the RPN centric crew were fiercely loyal as in the editor wars but would grab whichever was near me when we all were working a problem set; but I knew a couple of folks that hated RPN too.
It's possible, because of my undiagnosed dyslexia at the time, but I would grab the closest calculator, pause to see which is was and then start entering things as needed. But like Jon -- if I had the TI in my hands, I found myself copying the equation. I was trying to pay attention to what button I was pressing to check for any keystroke entry errors. Both types had all of the same math functions so there was little difference in the number of strokes, other than not needing parentheses on HP and how you entered the calculation. With the HP, I was more aware of that equation I was calculating because I was having to make sure I entered it in the proper order so I could get the right answer. In my case, I was probably a tad more careful because I was being forced to thinking in terms of precedence - but I was thinking about the equation. Whereas with the TI I was just hitting the button per the equation on the paper. I typed a tad faster on the TI than the HP because I was not thinking as much but ... I probably made more typing errors there because I thought less about what I was doing.
Clem