Enyalus
MALE DOMINANCE!!!
I can see both your points. In my opinion, the Jedi Side's talent pool is deeper than the Sith, so I'm going to offer up a few reasons why the Sith Lords might be able to emerge victorious (in no particular order):
Although Nomi has shown the ability to use Force Sever, she's only done it once to a very distraught opponent (see Faunus' post).
Furthermore, Sion wields an advanced version of Force Drain, so it might be a matter of who can get their attack off first.
Sion was also the leading Sith Assassin of the era, meaning he knows how to mask his presence in the Force. It may or may not be a factor in deciding whether Nomi will be able to Sever him.
In addition to Bane having his orbalisk armor, Krayt has his crab armor (which is also lightsaber resistant, and covers most of his head).
Krayt was a general in the Clone Wars and a master of Jar'Kai, so he has considerable lightsaber skill in what era Lucas referred to as the Jedi at their best.
Home field advantage, so to speak - Ziost is heavily steeped in Dark Side energy.
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All that being said, I'm still not exactly sure how this would go down. If I had to guess, right now my opinion would go something like:
1. Sabers - Sith Lords. 8/10.
2. Force - Jedi Masters. 6-7/10.
3. All-Out - Sith Lords. 6-7/10.
Pure sabers, the Jedi would have a helluva time getting past Sith armor and the practically immortal guy, especially on Ziost.
I see the Jedi taking the Force contest by a small margin. One reason is Nomi's Force Sever if she is able to use it. However, she's also a master of Force Light, which weakens Dark Siders ability. Plus, the only one who can contend with Yoda's pure Force ability on the Sith team is Bane. I'd have given the Jedi a bigger majority with regards to the Force contest, but again - home field advantage. We don't know how much of a boost the Sith would get, but suffice to say it would be considerable.
Overall, I gave the Sith a small majority due to their durability and the fact that they're very close in terms of mastery of the force. Though, my ratings could be subject to change. This is my initial opinion of the battle.