I've read the Wiki article and researched the internet, but can't get a practical handle on what the difference between these two jobs are.  They give 2 separate oscars for these jobs, so they must be different, right?  And how are these guys different from production sound mixers/recordists?  Sound section of the crew credit is the most confusing of all.

Well I'm no expert, but we have a fellow user who is: schaumi. You might try contacting him.

Good luck!

DJ