I think you have expressed the nature of the problem very well. In my own experience of printing, and as someone who looks at others' "identical" prints in different sizes, I believe those never feel identical if the size difference is significant, unless the viewing distance is also adjusted a lot. I can make an 11 x 14" that looks pretty much like a 12 x 16", but an 8 x 10" will usually feel compressed, subjectively sharper, and more contrasty than an identical (in terms of matched exposure and contrast) 12 x 16". I suspect this is due to the perception of larger single-tone areas, viewing distances, and the angular viewing experience that a print's size influences, ie. how much one feels surrounded by it, as opposed to looking straight at it. Further, contrast and the feeling of sharpness are intertwined, and I suspect that our mind is more sensitive to minute differences in resolution than our eye would lead us to believe. I think we have all seen how difficult it can be to judge low sharpness vs low contrast, where the difference between them is a close one.
Originally Posted by tkamiya
Unfortunately, I belong to the group that seems to burn paper in getting the print fine-tuned. Indeed, most of the waste comes from improvements to dodging and burning, but there are small changes in contrast involved in the process. I usually end up with a print that satisfies me after an average of 7 sheets, during the initial session, all in the target size. Often, a follow-up session, or two, are needed to improve it further. On a rare occasion I needed 15 sheets, and I have a few prints where the 3rd one was right.
I have not succeeded translating the feel of a smaller print to a larger one without having to rework it. I have used RH meters, and other types of darkroom automation, which can be very helpful, but the best results come from the most basic, technology-free approach, like that described by Doremus and Michael, in this thread.
To make things easier, I now try to print everything in one size, as 12 x 12 or 11 x 14, occasionally as 12 x 16.