Here's what I found on the subject, plus some personal recommendations. (I'll simply write about lists, because what is relevant for
itemize should also be for
Schlosser, Wissenschaftliche Arbeiten schreiben mit LaTeX, recommends the use of LaTeX's standard list environments for lists with items spanning several lines each, but advocates using the starred environment versions provided by the
mdwlist package if list items are short. (Those starred versions have before/after spacing similar to the standard environments, but the spacing between items is equal to that of
compactenum, i.e., no extra space.)
Bringhurst, The Elements of Typographic Style, states no explicit rules for list spacing, but the lists in his book don't feature extra space between items. The spacing before/after lists varies from no extra space to either a half or one line of extra space (note that Bringhurst often uses typographic variation to give implicit examples). The lists with extra space before/after them presumably start/end paragraphs.
Personally, I would use either no extra space between list items (as I'm a fan of grid typesetting) or at least spacing somewhat smaller than that of LaTeX's standard list environments. The before/after spacing should depend on whether a paragraph starts/ends, and this should be easily discernible (which again means modifying LaTeX's default spacing -- reducing
\topsep, but enlarging
\partopsep). I emphatically disagree with Schlosser's practice to vary the spacing between list items dependend on the item's length, because this produces inconsistent document layouts -- lists are lists, and if you deem the extra space ugly for some lists, get rid of the space for all lists.
Neither Schlosser nor Bringhurst mention or show examples of "as-paragraph" lists like
asparaenum. A possible use is some kind of step-by step argument/proof, with long individual items (possibly spanning multiple paragraphs), and the whole list spanning multiple pages -- in that case, it may be wise to de-emphasize the "list-like" look.