Casino Royale is too long, Quantum of Solace is too short...I'm really hoping Craig gets a third film that's just right.
Actually in many respects I prefer QoS, if only because I can find the time to watch it. Seriously if I have 2 1/2 hours free I'm more likely to watch OHMSS!
I think they do work well togeather, and I especially like how CR begins in snowy Eastern Europe and ends in sunny Italy and QoS starts in Italy and ends in snowy Eastern Europe. I also like that at the start of CR Bond can't see the bigger picture..."I thought one less bomb maker in the world was a good thing." yet by the end of QoS he can see the bigger picture to such an extent that he doesn't kill Vesper's boyfriend.
I think for me what lets CR down is not just the length, but the structure--there's nothing wrong per se with having your action sequences at the start (see Empire) but when you have a running theme of mano a mano--cobra vs mongoose, Bond vs free runner, Bond vs bomber, Bond vs Le Chiffre (even Bond vs the African guy since he offed his bodyguard so quickly)--then to jam in a final fire fight which has Bond vs, er some guys, kinda spoils things. It is like the producers didn't trust that people would have gone for a Bond film without a big fight at the end. It doesn't help that there's so little romance between Bond and Vesper, and that it mainly comes towards the end, romance is fine but at least in OHMSS it was more obvious and came in earlier.
CR really does hit you over the head sometimes plot wise: take Mathis' cringeworthy aside to camera explaing the rules of poker and that Bond has spotted LeChiffre's tell, or 007's really lousy detective work in making it to the health club in the Bahamas where he finds (conviniently) CCTV footage flagging Demitious, wow lucky that camera was pointing in the right place eh? Contrast that with the clever way in which Bond tags Green and co and follows them to Austria. And therein lies the major difference. In CR the plot is explained to us; at great length, just check out M's clumsy line about how Le chriffre can set up a high stakes poker game at casino Royale in montenegra (which is in the former yugolsavia she might as well have added) QoS on the other hand requires you to think a bit more.
Now how much of that is intentional I don't know. CR is very polished whereas QoS is not, but that might not have been the original intention, remember the writer's strike probably entailed that the QoS script was maybe a draft or two short of where they'd have wanted it, as such QoS is quite rough and ready but I kind of like that.
For me QoS feels a bit more like a Bond film, a touch more humour (very deadpan I grant you but that suits Craig) a villain with a diabolical plan, and a villain with a ridiculous hq...hello and welcome to my exploding hotel!

Plus Camille is quite interesting.
And herein likes another couple of problems I have with CR. The villain and the girl.
Le Chiffre. This guy is the bad guy? Funny cos for most of the film he appears to be the bad guy's accountant! And sorry but an asthmatic villain? He doesn't even have any memorable henchmen! Shame really as Mads was one of the only good things about Clash of the Titans. Don't get me wrong, Greene isn't great. but he just feels a touch more villainous.
And on to Vesper...Is she French, is she English? There's no need to decide because clearly Eva hasn't!

Her character doesn't develop much. She's a bitch and then she isn't and loves Bond. Now in fairness I blame Fleming because even in the book the girl makes no sense! There's never any indication of why Bond would fall in love with her unless it was the fact that she didn't fancy him! I think as well Eva just doesn't ever make Vesper seem vulnerable enough. I wish they'd hired Rose Byrne she'd have made a better Vesper (and probably would have had a better accent).
Oh yeah, and how come Le Chiffre was still so bothered about the money even after Bond handily killed the guy he owned it to?
I'm sorry, the above makes it seem like I hate Casino Royale and I really don't, I just think its flawed and somewhat overrated, by the same token Quantum of Solace is somehwat underrated.