I suspect this is going to be difficult - but maybe I'm wrong! I suspect a lot of it has to do with proportions.
For example, I have shorter legs. Well, technically speaking they are proportionate to the rest of my body and not really short for my body - but modern fashion calls for really long legs in proportion to your upper body. Therefore, to elongate my legs, I look for tops that are shorter - hit at high hip. But this is just *in general.*
This works great for skirts, trouser cut jeans and slacks, and bootcuts. However, for skinnies, I look infinetly better with a longer top. Except then I seem to also need heels too... esp if the top is as long as crotch point (i.e., longer the top, higher the heels).
Clams: are really skinnies cropped off below the knee. I have worn both shorter and longer tops with these. For some reason, they can go either way. Probably look a tad better with a little longer top.
Shorts: I only wear shorts as "gear" because the only shorts I look good in are fairly short - 4 inch inseam - and in my 40s my legs have seen better days. But for shorts the only thing that works is a shorter top - skirt top length.
Miniskirts: you didn't ask, but I do think these look better with shorter tops. Unless you have infinetly long legs.
I will look forward to Angie's response. I am imagining there are some generalizations but ultimately it's one of those things that's unique to one's own proportions?