I run Franco's on Codename and get good battery life (about 40% left around mid night), but sadly, battery life is relative only to you, how you use your phone. and the apps you choose to run. I suspect that most of the popular ROMs and the popular kernels are within a few percentage points of each other in regards to battery drain (given that some of the crappy ones may not fall into this category).
Where you see big differences are from one guy who runs any ROM/kernel combo and plays video games or watches netflix for 4 or 5 hours a day and says the battery sucks, vs another guy who has the same ROM/kernel and only has 1 hour of screen time and says it's great with 48 hours of battery life. My opinion is to run whichever you like best, whichever seems to make your phone run the fastest, and your battery life will be pretty close to the same, regardless of what ROM you're using. Some may disagree with me, but that's why I called it an opinion, not a fact. So far, no matter what ROM/kernel I'm running, I do the same things with my phone and get the exact same battery life.