It's a long and very detailed report.  If you read German, or run it through

Google Translate, you can read the entire report:

 

Here is a summary:

33 ball heads were run through extensive performance tests.

The ball heads were divided into 3 groups and scored on a 100-point scale:

 

Under 100 Euro (<$150):

Sirui had the top 3 out of 11 tested.  Closest competitor was 23 points below the top Sirui model.  Sirui's winners were G-10, G-20, C-10 (included with T-005 / 025 travel tripods).

 

100 - 200 Euro ($150 - $300):

Sirui ranked #1 (K-20) and #3 (K-10) out of 12 tested.

The Sirui K-20 scored 89 points -- the highest score in this price category and the second highest score in the entire test.    

 

Over 200 Euro (>$300):

Sirui had none in this category.

The only ball head to score higher than the Sirui K-20 (89 points) was Manfrotto 468MGRC4 at 90 points. The Sirui K-20 supports 55 lbs and retails at $175.  The Manfrotto supports 35.3 lbs and retails around $300.  So, the Sirui holds 55% more load, yet costs 42% less!