NxBRE embeds two engine flavors, the Flow Engine, which is basically "programming in XML" (ie flow control, loops, subs in XML) and the Inference Engine, which performs deductions based on facts.
To decide between them, one criteria is the skill level of the person who's going to write the rules: are they more confident with a procedural approach or can they understand pattern matching and inference?
Another criteria is the level of integration with your application's objects: if you need to perform a lot of interactions with your objects, the Flow Engine is better. If you can reduce these interactions to a few touch points (say convert account to account facts and then back), the Inference Engine will work fine.
HTH
David (NxBRE's Lead)
PS. I've found this question by accident, usually people ask on SO:
http://stackoverflow.com/questions/tagged/nxbre[
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