I have an InDesign file with a number of vector images in it. I was wondering whether it made any difference whether I exported a full quality version and compressed the resulting pdf or exported a lower quality version with no subsequent compression. Is there any reason to choose one over the other?
In general, I've found that opening the exported InDesign PDF with Acrobat and then resaving using
Reduce File size . . . in Acrobat results in smaller files without any significant loss of quality (for proofing). I use a custom Job Option when exporting from InDesign for proofs. The custom Job Option is slightly better than the "Smallest file" option -- images down sampled to 125ppi, no bookmarks, hyperlinks, etc.
I never recompress PDFx files or PDFs destined for production. But I do resave every PDF as a reduced PDF when sending PDF proofs. I actually have an action set up to reduce and save.
InDesign (or Illustrator or just about any app) will tend to embed native application data within the PDF regardless of the job option settings. While the basic Job Options are the same, when you resave the PDF as reduced using Acrobat, Acrobat throws away all this hidden native app data it doesn't need which can save a significant amount of kilobytes at times. Of course, the nature of the content has a great deal to do with how much, if any, size is reduced.