I don't own yet those libraries. However I maybe can help you a bit.

Andromeda is the full orchestra, you can see the "free Big Bang orchestra" as the demo of Andromeda. It's the same but much more complete. That's a library, according me, is mainly useful to make quick sketch (because you play the entire orchestra at the same time), you can play it for fun or use it to add accents in a piece.

Zodiac is 7 massive ensembles: 1 & 2 violins/violas/cellos/basses/horns 12/trombones. It's a package more versatile/complete, it's very interesting to add this special "massive" flavour in a piece.

They are not comparable, they are very different things.

As they are already many legato combo in BBO, I'm a bit skeptical in what a Legato Performance Combos can bring new in the table.

I think child choir could be a nice contribution in the collection, as I suggested in Ganymede, a patch "short with random syllable" would be really awesome.

And the cherry on the cake, like some said, a pack with all "big scores" missing instruments (Harp, Sax, etc. and maybe some original like an electric guitar)