That would be the Yuuzhan Vong, but they were only the Borg-equivalent because they were "outside of the Force." They couldn't be sensed by the Jedi, nor could they be affected by most Force powers.
Oh, a friend of mine continually insists that Star Wars is better. There is a Wars equivalent to the Borg (power-wise), I just don't know what it is.
In a fight, Wars almost always wins. Ships are bigger and immensely more powerful.
Now, if you really want to get into this, I would be glad to, because nerd arguments like these are my bread and butter. If not, just ignore this post.
The borg would assimilate all of the clone/storm troopers.
This is assuming say, one (or a few more) Borg ship(s) versus one battalion or whatever of clones with a single Jedi General.
When facing the Borg, it's all about the tactics. Star Trek developed modulating phasers, and who knows what some lucky SW tech whiz could pull out of their ass? So, let's assume that the Borg are here, and the Republic has a reasonable technology to fight them. Firstly, they have the immense advantage of the Force. It would be quite a mean feat for a Borg ship or fleet to approach any Jedi without them knowing it... that kind of hive mind must screech at their senses. So, before the battle even starts, the Clones have the Force on their side, which practically means they get a "One Deus Ex Machina Free" card.
Secondly, once the battle begins, the Clones themselves are a honed fighting force the match of few others. They're trained from birth in tactics and weapons... ever see Clone Wars, the cartoon? And there was that one badass squad of Clones running around and blowing the phlox out of all the droids? It'd be like that, only instead of like eight guys there's thousands of them. This is an army bred to fight. It has no other purpose, and they're fanatical. A Clone has three obligations, in this order: the Republic, their General, and themselves. They can, have, and will sacrifice their lives for the good of the Republic. So if that means slamming a small, elite squad into a Borg cube on a suicide mission to blow them all to kingdom come, then that's exactly what they will do, and, knowing the general badassery of Clones, some of them would probably survive.
The Jedi, on the other hand, would wreck Borg. Borg combat strategy: 1. Approach enemy slowly, like zombies. 2. Hope adaptive shields keep you alive. 3. Eventually capture and assimilate. This is a strategy that works well on the closed decks of a ship, where there could be a Borg around the corner waiting to dramatically grab you, but what major battle is fought inside of a ship? Okay, Tantive IV, but what major, large scale battle is fought on a ship? Anyway, the Jedi has all the time in the world to wreak the Force upon his/her enemy. A properly trained General (and you have to be a Master to be elevated to that level of command) would be doing a pretty terrible job if the Borg ever got near him/her.
Thirdly, technology. I wish I knew where that one website was that calculated the Joules of the average blaster versus the average phaser. The blaster wins, anyway, and I'd imagine a disruptors the Borg uses are roughly the same output as blasters (probably higher, but not that high... I mean, if they were, they'd destroy the Enterprise's shields every time they were used). Now put those blasters on fighters and let hundreds of fighters go at the cube. It'd be like Wolf 359 only less Sisko and more explosions and smaller ships. I don't know the tactical use of fighters in combat (ask Worf) but I'd imagine it's damn hard to get a phaser lock on a tiny, quick thing like that. Really, I'd imagine they'd only be feasible on a ship without shields (do Borg ships even have shields?) but shields are meant to withstand a certain amount of energy, and blasters are higher energy than the energy weapons of Trek. Couple that with the ship that is probably going to be nearby (where do you think those fighters came from?) and you have massive cannons firing at you, too. Really the only thing that Borg have going for them is their ship regeneration (useless against the barrage of the myriad fighters) and assimilation, and assimilation is next to worthless if you think about it. Borg never run at people. If the Clones can't fight them, they will retreat. They're not Klingons, they're not going to charge into battle to die. Best to preserve yourself so that you may preserve the Republic.
Not to mention that, from a meta standpoint, Borg are the villains and therefore are supposed to be defeated.