Not ready to give Firth the nod over Franco yet, but those 2 are neck in neck IMO. You have the British period piece, and you have the guy acting and carrying a movie by himself. Both amazing performances which carry a film, and both are portraying real-life people, which the Academy loves.
However the flick itself is really well done...and this is coming from a dude who pretty much yawns when "British period piece" or "film about royalty" is ever brought up. I liked it quite a bit, and everyone was great in it. I thought Firth and Rush had amazing chemistry.
It's likely the favorite to win Best Pic, I'd think.