Well if it was the Homeworld Gems, then I believe they would easily defeat the ponies of Equestria due to their extremely advanced technologies.
But of course, it'd really depend on the ponies present in the battle and what powers they have, because someone like Discord (although not a pony) would be easily able to mess with the Homeworld Gems just due to the fact he's him, but that'd also have to rely on his willingness to participate.
Of course, we also don't know just how advanced the Homeworld Gems are too and if they possibly have technology that could nullify the effects of magic, since they have weapons that can tear Gem Fusions apart, so it could be safe to say they've perhaps developed other tools to deal with other situations since the Homeworld Gems have expanded their empire to other planets.
So I'd like to side with the idea that the Homeworld Gems would win this battle, but hey, I could be wrong. Still, this is an interesting idea to think about, nonetheless. :3