There's another part of the spam issue which can cloud the understanding, and that is the fact that there is no "standard" for scoring spam.
We use one standard, and it works well for us. Our "standard" does not include external spam filtering, so, attempting to explain how and why our scoring works, or, in case you don't agree, doesn't work, is like comparing apple juice to brake fluid - there's nothing to correlate between the the two, and, therefore, no real comparison, except that both are fluids.
Spam filtering is not only dependent on whether you are using external filters, but how the external scoring and weights are configured, how the internal weights are configured, and how the "triggers" are defined -- and interact with each other.
While I realize that my comments may server only to confuse further, and I do agree, the log results format in SmarterMail (which used to wrap in the search window, and haven't since about version 10.7 [approximately], they can be downloaded and searched with other tools. SmarterMail's 14 also brings the capability to search multiple dates, and that can help resolve issues which, otherwise, might escape notice, when dealing only with a single date search when trying to resolve delivery and spam issues.
Finally, remember that there are also some very nice log parsing tools which are available via a quick Google search.
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