You ask tough questions, lol. I was hoping you'd get tough answers.
All bragging rights are important to Clanners, especially when it comes time for Trials of Bloodright and Trials of Position. I think being part of the invasion of the Inner Sphere was a hogh honor so a warrior's accomplishments during Revival would take at least some precedence over another's accomplishments in the Home Worlds, generally speaking. It largely depends on the accomplishments in question and how important they are to the Clan.
As for your specific example/question about a Ghost Bear warrior having killed multiple abjurred Nova Cats and whether or not that stacks up to killing a similar numver of Hell's Horses, it's probably just about the same. Maybe a bit less, but both are considered enemies of the Clan. The difference is likely very little.