I don't mind having Lilly in charge. If you side with her, she really softens up towards you. First and foremost, my Lee is a solid role model to Clem. Lilly puts the group first, whereas Kenny acts on what he thinks is best. It's not about taking risks, it's about taking unnecessary risks. Did checking the barn REALLY achieve anything? Couldn't Kenny have waited a little longer in the meat locker? Why not MAKE A PLAN before running off unarmed after these gun-wielding maniacs who clearly have no qualms with killing the non-undead? Lilly keeps everyone going, Kenny makes a mess, my Lee picks up the pieces.
I think there will be a divide between Team Lilly and Team Kenny (in-game and on these forums, no doubt) and, unless Carley gives me a convincing argument to the contrary, I'm thinking Lilly is the one I should stick with. I think she's going to be ridiculously loyal to and defensive of the group instead of Kenny only caring about his immediate family.
If I had to put money on the cause of the big argument in the Episode 3 trailer, I'd say it's something to do with Kenny's family. If there was anyone able to "screw it up for everyone," it'd have to be Kenny or Duck, right?