I rarely use the style variables (style properties) myself. Extra.css especially for the navigation is your friend. Plus, working in the style properties I find takes far too much time when you need to keep switching to different pages and insert code into different boxes.
Extra.css is definetely going to work for you better than the style properties. Some parts you'll be best using but for most EXTRA is better and sometimes if not most necessary as stated above especially if your wanting to create a custom navbar, modify your profiles, style certain sideblocks differently etc.
After reading that I think I'm not so surprised because like me you probably want to style stuff extensively and the extra.css is better, plus you get work done faster with an array of other benefits.