rootSU - I get what you're saying about serials not meaning hardware revisions, but isn't that confusing?
As was pointed out by tylerdurden83, there was a GPS issue which was found on 310k models.
If this issue was fixed on that same 310k batch (and we can safely assume that it was), then that same issue has a much lower chance appearing on a future batch (small chance of the same issue returning after something was done to prevent it). Not to say new different defects wont start appearing.
You said "there is no relevance to the serial number", but by having one batch you probably wont have the defects of a different batch.
If I could minimize the risk of having a GPS issue by not buying 310k models, but still may have rattle of screen issues, I would prefer that.