I believe that with larger formats, for a given FOV, you are always closer to 1-1 repro size, which gives a different look ...
That is only of much significance in the close-up range, where that the magnification is more than about 1:20 (this is the typical guideline in optics literature for when the simple optical guidelines for comparing DOF and such between formats break-down.) It is not going to be a relevant difference between MF and smaller formats at ranges more than a few feet.
[EDIT: jsch explains some of this too; I add that when the larger format is DMF instead of 10"x8", the threshold distance for being "pretty identical" is reduced in proportion, to about 2 meters. But do not take the "1/3 of DOF in front, 2/3 behind" literally: the specific numbers are meaningless as they depend on many factors, and the statement is just an indication that "more is acceptably in focus behind the plane of exact focus than in front".]
Also, another effect of format differences is that it makes spherical aberrations (and aberrations in general) at equal f-stop worse in larger formats, because light passing though near the outer edges of the aperture is reaching the lens further from the center, and so the angular variation between the paths of different rays from the same part of the subject is greater. That is, the incoming cone of light gathered from each point of the subject has a wider angle. (The strength of various aberrations vary in proportion to various powers of this angle.) In fact, in partial contrast to what jsch says, a simple linear scaling down of a lens design to get one for a smaller format covering the same FOV and with equal minimum f-stop gives less aberrations at equal f-stop due to these reduced angular variations.
On the other hand, when one uses a proportionately lower f-stop in the smaller format, for example to get equal DOF or equal shutter speed at the lower ISO speed usable in the smaller format, then the range of incoming angles is equal, so that disadvantage of the larger formats goes away, and the lower minimum f-stop designs probably require more careful correction.
And yet again: with equal FOV in different formats, and far enough from the subject that the magnification is less than about 1/20 (i.e., subject distance about 20 times focal length or more) the transition from sharp to unsharp is determined almost entirely by the effective aperture diameter (entrance pupil diameter), which is the ratio of focal length to f-stop. Format size has almost no inherent relevance to this except in "close-ups". Please search out and consult any of numerous sources on lens optics, such has online lecture notes from various reputable universities, if you need a detailed explanation of that.