"odds makers favor Rousey" is the kind of headline designed to draw bettors interest... probably because the "smart money" guys figure everyone knows/has heard of/likes Ronda while Nunes is pretty much unknown to the 'man on the street' who doesn't really follow MMA and only knows Ronda Rousey from Sports Illustrated (nude body paint or other issue with Ronda's pic).
Plenty of ordinary folks will likely put their money on Ronda, but the "smart guys" will probably bet on Nunes.
In the end, the "odds makers" are only interested in making odds to encourage the MOST people to bet ON SOMEONE... so they can take their percentage no matter who wins the actual fight!
Personally, I don't think Rousey will do well....but I think the organizers would like nothing better than for Ronda to win which would let them gen up another several fights with big box office sales. Nunes, Holm, et. al., aren't going to sell nearly as many tickets as Rousey (on name recognition alone).