All Eley is the same, it just depends on how it shoots in their test barrels as to what lots become Target, Black, 10X, etc. I don't know that you can draw any conclusion other than Eley is first rate stuff.
Eley has alt least two bullet styles, flat point and round nose.. I know Black is Tenex that doesn't shoot to spec, but I have no idea about the rest. For that matter, Remington loaded some Eley ammunition for U.S. use, but Eley continued to import it;s whole line.