Main Question: ignoring the size of the illustrator file, when you save the file as a PDF, intended for commercial print, what are the absolute best settings possible?
Before answering “Press Quality Preset,” (thank-you I know that already) maybe I should provide further detail. Where to begin...
This was the initial hitch that prompted further inquiry
I was trying to save an illustrator file (CS6 in case that makes a difference) as a PDF for print. Naturally I selected the Press quality preset. However, when I examined the settings for this preset, I found that my ‘Color Bitmap Images’ are using a JPEG compression. Sure the Image quality is set to the maximum, but it’s still a JPEG compression- thus prone to image degradation if it needs to be resaved (or at least that’s my understanding). It seems reasonable that the simple answer would be to just change the compression from JPEG to the only other option- ZIP, in order to maintain the quality. Duh! 
However, I’m left wondering why JPEG is the automatic choice for the press preset if the ZIP compression provides better quality (possible answer- File Size). Furthermore, if the compression setting is not actually set for the highest quality possible (in an attempt to keep the file size down), then what other settings have been lowered in addition to this one.
My hope, as a result of posting in this forum, is to create a new PDF preset in illustrator that will optimize the quality of all possible aspects for any illustrator document. For ***** and giggles let’s just assume the document was originally created with an 1/8 inch bleed, using CMYK color mode, and a 300 ppi raster effect. Plus, this document has utilized every aspect of illustrator in some way (no this is not a real document- but rather a hypothetical document that is being used to identify the best possible settings available, no matter what the content is).
Will these settings be overkill for the majority of documents created in illustrator? Yes! 
But that’s not the point- the point is, I’m exhausted 
of having to sift through mountains of information, to figure out the reasonable and the friendly-file-size settings I “should” use for every document I create.
Now, I’m just looking for the big *I WIN* bomb that’ll cream all future documents, regardless of the content, transparency, effects, fonts, etcetera… etcetera (that’s a fact).
Maybe I could’ve skipped the story- but it just seems like people always end up having to go back to explain themselves anyway.
Input on... any of this would be greatly appreciated