I have been on both, and for me personally, the levimir works far better. My lantus seemed to "run out". I used to take it in the morning, and would wake up with high blood sugars quite often. I am now on split dose levimir (I am a diifficult case, and never had a 20% HbA1C, but di have a few 9s and 10s a while back. I am now running between 6 and 7, although this is result of a lot of effort, as well as the insulin switch. I would say, if whet you are using works, stick with it, and if it doesn't give the other one a try....you never know. God luck