We use both the A-16II and the A-16R. The A-16R adds the following features not available in the A-16II:
1) Add in a 17th channel. No extra mixer required. It is an analog stero channel, but you can add in without burning one of the common 16.
2) Ability to add inserts (like EQ).
3) Keep all the big hardware in the back out of the way. You only have to have one simple CAT-5 wire to the A-16CS which I mount on a mic stand. No wall-warts or power cables.