I'm confused that people use "big and yet small" rather than "big yet small." The reason I find this confusing is that but, which kind of resembles yet, is used differently--"big but small." Why can't I just say "big yet small?"
There is no harm in saying 'big yet small' but bear in mind that one is trying to emphasize the oxymoron, and this purpose is better served by using slightly more colourful and detailed differentiation between the 'big' nature and the 'small' nature of the object/subject in question.
For example, 'big and yet somewhat small' sounds more dynamic and compelling than 'big yet small', despite the latter being shorter and grammatically correct.