The Eastern Orthodox, denying that the Spirit is from the Son, ultimately deny that the Son’s generation was unique; and consequently, that the Son is the only-begotten Son of God. Augustinian Trinitarians who, unlike the Eastern Orthodox, believe in the Filioque clause, are still in the same boat. As much as they would like to say that there is a difference between “generation” and “spiration,” no meaningful distinction is actually made. The Enlightenment-era Homoians, such as William Whiston, on the other hand, have actually provided a meaningful distinction between the second and third person’s derivation from the Father:
Jesus Christ is in a peculiar sense the Son, the only, the only-begotten, and the most beloved Son of God, i.e. a Divine Person in an extraordinary and singular manner deriv’d from, and peculiarly near and dear to the Supreme God the Father. By the extraordinary and singular manner of the derivation of the Son from the Father, I mean, at the least, that he, and he only was deriv’d from the Father αμεσιτδιτως, immediately, and without the least ministration of any other being: which was only true of the Son of God. All the subordinate creatures, nay, the Blessed Spirit himself, being deriv’d indeed originally from the Father, but not without the ministration of the Son; or, in modern language, which will bear a true sense in this place, proceeding from the Father and the Son, or rather, from the Father by the Son.
Source: Primitive Christianity Reviv’d (Volume 4)
Note: Updated archaic capitalization and italics.