BSG is some pretty heavy drama. Main characters shoot each other. Heroes shove bad guys out of airlocks. Heroes order the summary imprisonment of other heroes. Cute, spunky fighter pilots get shredded by gunfire, burn alive in their cockpits, and suffer drug-fueled emotional breakdowns. Firefly, on the other hand, has Jayne (whom I f'ing love, btw - "I told you to just scare him!" "Well... Pain is scary...").
BSG also makes more use of the lengthy screen-time available for creating involved stories and exploring complex characters, but at the same time it doesn't mess around with slowly-unfolding "mythology stories" like The X-Files used to. Miss an episode of BSG and you have to spend your lunch break surfing the web, trying to find out what happened. Firefly has an episodic story-telling style, miss an episode and nothing much will have changed when you return. Heck, they were shown out of order the first time around, and a lot of people never noticed.
Unfortunately, all of that makes Firefly a better choice for a network executive. Comedies, or "dramedies", are much more accessible to the public. Shows that require constant attention, shows with intricate ongoing plotlines, have a very difficult time attracting new viewers. Firefly would be easier for a new viewer to jump into mid-season.
Firefly is also an adventure show, where Galactica is a drama and, for better or for worse, most people associate science fiction with the former. This means that the people who didn't like Blade Runner "because it was boring" will be annoyed when three episodes of Galactica in a row end with no gunfire or dog-fights or robots. At the same time, lots of people who "don't like science fiction" will simply never give Galactica a chance, in favor of yet another police or medical procedural show.
The SFX of the two shows support their particular spin on sci-fi. For instance, exterior shots of the Galactica show a gigantic tin can, unmoving, floating silently in space. Meanwhile, exterior shots of Serenity show it engaging its afterburners and accelerating loudly away from the camera. The most recent episode of BSG featured a gripping dogfight during which the viewer gets to see...
the crew of the ship's Combat Information Center staring at their displays and not speaking. It was awesome.
As a fan I prefer to watch Battlestar Galactica, without a second thought.
As a network executive, I'd give Firefly the green light.