Last I checked, Traya doesn't really have an army. She has a group Sith Assassins and the Academy on Malachor V. She has no fleet, and the only means of travel that she had was when she jacked the Ebon Hawk. The Ravager was under control of Nihilus. Her 'army', if you can even call it that, is more like a small cult of followers. Revan, as a Jedi Knight in the Mandalorian Wars, was in command of a third of the Republic Navy. That's a substantial force.
Revan as the Dark Lord of the Sith, had an army consisting of what remained of the Republic Forces that followed him, as well as others who joined his cause after he fell to the Dark Side from Darth Vitiate's mind scrambling. According to the Revanites, during this time Revan trained a Thousand Dark Apprentices. As indicated, he either found Force Users and had them trained on Korriban, captured Jedi and converted them via torture, temptation and psychological tactics, or Jedi who willingly converted.
Some say Traya wins a space battle. That's quite impossible for her to do without a navy. Sure, she has her Sith assassins with stealth fields. But they need ships to board with. The reason why that ship at the Paragus Mining Colony was overrun, was because the Sith Assassins were on board the Ebon Hawk when they picked it up, and that's how they infiltrated. Now, even assuming such a tactic worked with the army under Revan's control, after one or two "Mysterious Losses", Revan would initiate new security measures and tactics that would nullify the Assassin's ability to infiltrate his vessels, thus eliminating them as a threat in space warfare.
It's already been indicated that Revan is a tactical genius and possessed great charisma and leadership skills. Traya herself was infatuated with him and Revan evolved the Republic's tactics and changed the face of warfare to combat the Mandalorian threat. Moves that were so surprising that Mandalore was thrown for a loop.
Revan's forces during these times beats Traya for numbers 100-1. In terms of personal power and skill, I can't even conceive of a time when Revan wasn't always more powerful than she was, except if it was Before he became a Jedi for the first time. As the Revanchist, as the Sith Lord, the Prodigal Knight or as Reborn Revan, he has always appeared to be at a level of power and skill tiers above and beyond anything Traya ever achieved.
Traya does have a fleet, remember the Battle of Telos IV? Nihilus didn't come alone, he had a fleet backing him. Basically Traya has what remains of Darth Revan's fleet, which is substantial enough for her stealthy/hit and run tactics.
And I don't know if your aware, or I've just misintepreted. But may I stress this is the Revan of the Mandalorians Wars - not Darth Revan. So he has no Sith, only Jedi. (which may I add, Traya could convert through use of Malachor and her Sith assassins) Your correct though, Revan does outnumber Traya in terms of forces. But I doubt this would be a straight up battle. Most likely Traya would use his forces against him, corrupting his Revanchists and making them fight against him.
Let's look at the possiblities at Traya's options ('cause options win wars):
1. She can sit at Malachor V and attempt to erode Revan's army slowly with. But as I've already explained, Revan's logistics are too good to be eroded like so.
Not as sound as you think. The Revanchists could easily be corrupted by Traya through capturing (via Sith assassins) and conversion (via Malachor) in this sense Traya erodes his armies by taking his Jedi, then uses these Jedi to erode his armies. Its an endless cycle of destruction!