Visually you can't get WYSIWYG, the difference in the output resolution of the two is significant.
Hi Andrew,
Besides the obvious differences due to magnification, a related but somewhat different angle to the question is; Does it matter that you can't get WYSIWYG?
I view the pixel peeping, zoomed in display view of pixel detail, more as a means to get an indication whether the sharpening does
any visual damage to the representation of organic micro-detail contrast and smooth tonal gradients. As long as the image structure doesn't 'break up' (which is an experience/judgement call), one can increase the amount of sharpening. As long as the structure stays intact, it cannot suddenly 'break up' in print.
Of course, there is also some loss in the print process, due to ink diffusion at the finest detail level, but that's why we want to sharpen as much as possible without going too far at the native printer's output level. We cannot make some materials look as sharp as others, because they are not capable to show the same resolution.
Important to note, I make a distinction between sharpening, which really increases resolution (by deconvolution and wavelet type of amplitude enhancement) of certain spatial frequencies, and enhancing local contrast, which is more taste related and suggests sharpness but that's just visual trickery.
The deconvolution sharpening part only has a single best setting, doing 'more' will break up image structure, doing less will leave quality on the table.
The visual trickery part is more difficult to get right, because it is more subjective and taste related, and its effect does vary with output medium diffusion. Here is were a bit of experience goes a long way. Luckily it has more to do with lower spatial frequency detail, which is less sensitive to ink diffusion.
Trying to get closer to a predictable preview by zooming out below 100% zoom is a very poor way of previsualizing
real sharpness, because of the down-sampling artifacts that suggest detail that isn't there. It may help a bit with judging the effect of the trickery kind of local contrast enhancement though.
Cheers,
Bart