things to consider/explain
first off, most comments on here, and that i will make are done with the expectation that ACCURATE is our goal. movies are edited on displays with specific qualities, and we want to try to match those qualities so that we see what were 'supposed' to see. it's completely your right too change settings to your preference, but be aware that makes you part editor, as you are changing the content to what you think it should look like.
that being said...
what dynamic gives you better blacks
-dynamic mode crushes blacks and clips whites. black is supposed to be at a level of 16, and white at 235. the dynamic settings might change black to 19 or 20, and white to 230. what this does is remove some detail in the shadows, and the brightest parts of the screen(bad), but it also compensates for poor settings a bit(good). if your brightness is set too high, then instead of getting washed out blacks in movie mode, you still get inky blacks in dynamic. the easy fix for that is of course to set brightness correctly. but sometimes it's the content itself that's messed up, and in those cases, crushing blacks a bit can look better. it's still not the best solution, but i believe this is why black would look better in dynamic. and as far as the bright end goes. if we change 'white' from 235 to 230, then everything else gets a little brighter. our eyes tend to prefer bright over dim whenever doing quick comparisons. however, you are losing out all the info between 230-235, and again, changing the way the image looks from what the director intended.
the best solution to this is to set brightness correctly, and fix the gamma. fixing the gamma will allow details to be seen in the shadows without washing out the blacks completely. it can also improve the bright images in the same way.
as far as the sharpness goes, most ppl recognize a goal of 1:1 pixel mapping. if each pixel is represented correctly, then that's the 'sharpest' the image can look. increasing sharpness does not increase resolution, it alters the image to give the perception of strong lines around objects. the problem is that the processing is 'dumb'. it doesn't know which lines are supposed to be thick and defined and which ones aren't. and when it makes lines more defined, it adds halos and other artifacts that can be very distracting. i know it sounds counter-intuitive, but you actually get a lot more detail, especially in the 'finer details', when sharpness is low. i've posted pics of this many times before, but here's another look.
sharpness set low
details are still 'sharp', stuff in the background that's supposed to be out of focus is out of focus. stuff that's in focus is smooth, doesn't have any halos.
sharpness set too high
we can see haloing start to occur. in the close up of the windows of the building, we start to see discoloration between the windows, even though the building should be a uniform color. we start to lose depth in the picture as stuff in the background appears more in focus than it should be
sharpness set WAY too high(to exaggerate what you're looking for)