Hi Dav,
The 3330 also uses the ultra-thin cal. 502. I don't mean to sound like I hate this movement or anything (I feel like I've been bashing it a little lately), but it's pretty far from a "work-horse" caliber and my priorities definitely lean towards chronometric precision and reliability these days. I do quite like the movement and find it quite beautiful and elegantly designed, just not ideal for a daily wearer IMHO.
The 5907 uses the Piguet 1150 with the automatic bits stripped off and a tasteful rear-mounted power reserve installed in their place. The movement is much more attracitve than the one they show on the Breguet website, as the one they show still has the bridges milled with rotor recesses (510DR), but the more recent versions of the movement "look" much more naturally manual wind. I think the latest version is the Cal. 511DR, which if I'm not mistaken has a slightly longer power reserve (96 hours compared to 72 hours) and a lower beat rate (21.6 kvph vs 28.8 kvph). Frankly I'd prefer the shorter power reserve as the higher beat rate makes the movement a little more consistent beteween positions, but I definitely prefer the flat bridges as opposed to the old style, so it's a trade-off worth making overall IMHO.
I hope I didn't confuse the issue with all the techy bits about the Ref. 5907 movement, in either and all cases I believe it to be more accurate and reliable (as a generality) than the movement in the Ref. 3330. Of course the Ref. 3330 just screams "Classique Breguet" and that is pretty hard to resist regardless of any practical considerations. 
_john