<br> is for line breaks. What you have is a line break.
The idea of using CSS for presentation is there to HELP you, not to force you to obey some rules other people make and force you to live under their rule, to your own detriment. CSS makes site-wide maintenance easier. Do you break address lines in many many pages? In other words, do you have that convention of presenting an address on two lines on alot of pages, and do you see yourself changing that in the future? If you use the block idea, in the CSS you could simply remove that block, and all those line breaks in all those addresses will bump back up. Easy change.
But do you have one address on one page you are breaking? If so, maybe it is better to use a line break. But then think whether or not you will expand the page to include many many addresses with two line breaks, that may eventually have one line. Just make sure CSS and HTML is helping your project, not hindering you just because some purists have a Golden Calf.