I think the only advantage deathstroke has is with pure speed of thought and calculations. Although it is significant, batman has so many more advantages in the brains department, examples include: science, deducing, verbal reasoning, vast amount of knowledge on various arts, preperation, inventions, intimidation, will power, initiative the list goes on. He's also no slouch in tactics/strategy (maybe on par with DS). Being able to use 90% of your brain doesn't automatically give you "knowledge", while batman feats in the brains department are unparalleled. What are your thoughts? I would say it is possible for batman to outsmart deathstroke.
Stroke seems to dedicate his superior intellect towards a specific area (combat, tactics, strategy) were as Batman is like a Swiss Army Knife of knowledge.
Stroke is like a surgical instrument used for one specific operation (combat)
And Batman is like the surgeon who can perform any number of surgeries using any number of instruments.