The logo portrays the identity of a club. Saprissa last year reverted to a more traditional look, similar to their old logo before the "dragon" shield: Tigres also changed their logo this year:
Let's see how long they last with the new one... (60s and part of the 70s) (from 76 to the start of the 90s, this is also the most beloved one)
MLS Logo History: http://www.mlssoccer.com/major-league-soccer-originals-logos That LA Galaxy "twister" logo... geeeezus. The wierdest one might well be the MLS logo on top of the page: I've heard that the original idea for the logo was red-white-blue, instead of the current green-white-blue. You can also get "ancient" MLS logos by going to the "clubs history" page, select a club, then go through the years at the bottom of that page: http://www.mlssoccer.com/history/club