[rules-users] Comparison info with other engines

I'm wondering if anybody has comparison info with other engines. I just started to evaluate the products not sure which factors to consider. But I have these requirements: Must Be 1)Free or inexpensive product. 2)Rules change frequently, level of effort should be minimum. 3)Multiple join condition (A rule is determined ranging from 1 to 10 data fields.) 4)Should support approximately 75 rules. Better if we have. 1)Change Rules dynamically if possible. 2)Ease of use for Business users and developers. 3)Rule versioning. Will be happy if any one can send me rule comparison document or suggest me which tools can i use to evaluate. Thanks, Lindy