I've owned and used both.
In my opinion, the Dillon is a more reliable precise machine. That said, the Lee worked for me when I was on a tight budget just fine. It just took some tinkering every now and then. I kept plenty of ball chain on hand. Mine seemed to like breaking the powder measure chain.
My choice now is Hornady. I sold the Dillon and picked up the Hornady based on what some friends have said. I love it and I'm not looking back.
"If someone has a gun and is trying to kill you, it would be reasonable to shoot back with your own gun." The Dalai Llama (5/15/01, The Seattle Times)
"That rifle on the wall of the labourer's cottage or working class flat is the symbol of democracy. It is our job to see that it stays there." George Orwell