Here are a few fun tables comparing Attendance figures of the MLS vs MLB.  I think you can interpret these any way you’d like.  My takeaways:

1. The Sounders are definitely a significant threat to the Mariners.
2. MLS and MLB are both losing audience in a bad economy.
3. MLB better figure out a way to retrench quickly.

Table 1: 2009 vs 2008 attendance stats so far.  Sorted by 2009 Avg Attendance.  Red is MLB, Blue is MLS.

Table 2: MLS and MLB Team Attendance Figures Interlaced, sorted by 2009 Attendance.

Notes: It’s obvious MLB still dominates, with only the Seattle Sounders breaking into the Top 20.  However, notice that the Sounders outdraw the Mariners so far, 29,536 to 27,234.

Table 3: YoY Attendance Changes so Far in 2009 (sorted by largest loss of audience).

Note: In this table, MLS is not alone in losing attendance.  Notice some of the big MLB cities who are shedding ticket buyers.  Comibined, out of 45 teams, only 11 are showing an increase YoY, and 6 of those are in the MLS.