All things being equal with the guns...I'd take the -3. The plus is that you will have no bushing issues and it will not have to be returned for the "M" fix if it has not been done already on the -1. I think the only other upgrade was the improved yoke retention system in the -3. I think the -3 would be the better choice.
Better yet....see if the guy can add them together and give you a -4, which many consider to be the best of the 686 batch.