¿Debo establecer una altura fija o usar relleno para establecer la altura de un fondo de texto?

I know this is probably a stupid question. But say I have a navigation menu, would it be more practical to set a fixed height..

 nav {
 background: red;
 Width: 80%;
 height: 60px;
 }

 nav ul li {
 Line-height: 60px;
 }

Or to use padding to define the height?

 nav {
 background: red;
 Width: 80%;
 Padding: 30px 0;
 }

I usually go with the first choice. But I'm worried that the font size might change in different computers/browsers and therefore becomes unproportional with the container. Could this actually happen?