I note that the two authors you cite are both English writers, and so the issue you bring up deals with how the English language acquired its extensive vocabulary.
While many of the words used in writing English are words inherited from Middle English (I will refer to this as stock English), a large part of English vocabulary comes from borrowings from other languages, in which Latin, Greek, and French predominate. (As an aside, other languages have striven to derive new technical terms from existing native vocabulary; for instance, the Icelandic words for osteoporosis and transmit are formed from Icelandic words that mean bone-thinning and throw out.)
There is a lot of overlap in meaning between these two groups of words. However, the stock English words have a more earthy feel, whereas the words derived from borrowed vocabulary tend to have a more clinical air to them.
In addition to this, it is often the case that the borrowing from Latin has a more generalized meaning than the stock English equivalent that would have been used in its place, and these more generalized terms are more abstract. This makes it hard for the reader to form a clear picture in his mind. For instance, if a man is trying to get somewhere and doesn't have a car, we can say:
Jack required transportation to his residence.
Jack needed a ride home.
The first phrasing sounds like something a bureaucrat would say in a report, and might be more appropriate there, but the second phrasing would make a much better opening line for a novel. Or how often has someone dropped something, and expressed his or her frustration by shouting, "Oh, feces!"
If in our writing we make heavy use of the borrowed terms, we may have the benefit of getting the exact meaning we are after, but it comes at the expense of being sterile in its impact, and it is very easy to get carried away with idea that the guy who knows the most words must be the smart one.
I have had the same impression from reading Orwell's essays as you have, and it does seem to arise from his preference for the stock English words over the borrowings from other sources. I'm guessing that this is a deliberate choice Orwell has made. (I can't speak for White, because I am not familiar with his work.)