I prefer no tan lines on someone else.  As for me, I'm too fat to go out in public wearing a bathing suit so I don't.  Last time I did, I was in the south, in Salvador, and I wore one because I had to (35 degrees +++) and hated every minutes I had to be seen in a "fat bathing suit"...  

  I couldn't wait until the evening so I could finally get dressed and cover up.
 
Sophie.