You claim that the longer format is more legible. I do not think it is necessarily the case, let me explain. (Another reason not to use the longer format is to avoid having too many pages in the paper, but others wrote enough about this, I think, so I will disregard this aspect.)
As a general rule, when writing either a book or a paper, I believe you should try to make it as easy as possible for the reader to distinguish which parts he should pay more attention to (because they are especially important, difficult or nonstandard), and which he can more-or-less safely skim.
In your example, the itemized format puts very strong emphasis on the notation used for various parts of the formula. This might be a good idea especially when you are just introducing this notation, and the formula (and its parts) are heavily used later in the paper. Or maybe you want to make sure the reader remembers exactly the factors on which delta depends.
On the other hand, it may be that the meanings of the symbols are standard/established earlier in the paper and you are merely recalling them. Or maybe you are never going to use them again in the paper. Perhaps the formula is just a side remark. In these cases, the longer format will (unduly) draw the reader's focus to it, so you may prefer to avoid it. In other words, while indeed this makes the formula itself more legible, it may make the whole paper overall less readable.
Of course, in practice, what you write may not fall into either of these extremes, and in the end, what should and what should not be emphasised is up to the writer's/editor's judgement and taste.