I think there would be a very 50/50 split on this kind of decision. Molly is clearly an excellent survivalist and will help you with such matters but regardless of whether you have a good or bad relationship with Kenny, he is your bro. You've been with him since the start, asshole or bff's it's gotta count for something. They've been through so much together than Lee and Molly.
So even after telling him to go fuck himself when he questioned helping me find Clementine at the end of episode four, I will still save him if I have the opportunity in episode 5 over Molly.
What's really interesting is that if you say to him 'Kenny, I NEED you.' He'll tell you to fuck off in a sense, but at the same time, he'll have the boat ready for Lee and will take him. Even though he's bit.