Smaller rings weigh less and require shorter (therefore lighter) total run of chain.
Larger rings wear more slowly and are slightly more efficient because the chain links don't have to bend as fast or as far as they come on and off the rings. (This was actually tested in a lab and reported somewhere on Bikeforums.)

Difference is probably academic, since it is possible that you will not be able to tension the chain with the available "throw" in the eccentric if you use rings of different size from what the builder provided as part of his design.