I've been wearing Levi's 505's since the 1960's. Recently Levi's changed the style of 505's from "regular fit" to "straight fit". The straight fit has a lower waist that I don't like.

I reluctantly tried 501's. I was nervous about the button fly.

However, the results were great; I really love 501's now. They fit me better than even the old style of 505's. The material feels stronger than the 505's. The button fly isn't a problem; just undo the middle buttons when you need access, there is no need to unbutton the top.