A good point of contrast is the recycled drydock sequence in Khan vs. the original TMP launch music. Both are great, but Goldsmith is going for epic and sense of wonder where as Horner is adventure and heroism. So whichever you like depends on what you're in the mood for.
The real point of comparison would be: What if Horner had to score a drydock scene as long as the one in TMP?
But generally I agree: Horner (who also did very nice work in Brainstorm around this same time) earned his chance to score TSFS and ought to have been able to do TVH as well - only (as I understand it) Nimoy was a pal and/or neighbor of Rosenman's, and gave it to him.