Levemir vs Lantus

What is the difference? My understanding is that their long action is caused by different ingredients. I have only tried Lantus. I read some people say it causes weight gain, which I don't need! I am reading other posts comparing the two. Any input would be great.

People say there duration is a little different. That Levemir is more flat and last closer to 24 hours. I have been on both briefly but I did not like Levemir, for me I got better control with Lantus. I didn't gain any weight on Lantus but like everything we are all different.