My best success (with Rio's in California) has been a jake/hen combo... I have had them run away or hesitate due the jake as much as I have seen them run in... One of the biggest tom's I have seen in the area I hunt, came in (I watched him walking down the dirt road), came around the corner, saw my jake decoy, and took off like I had shot at him (last day of the season)... I sure wish I had left the decoys in the car.
A single hen decoy has not been as productive... All too often they will hang up and display out of range and saunter off eventually (whereas I think they often would have kept coming forward with no decoy).
I do tend to use decoys in more open country (for me that is pastures or meadows)... In wooded areas, I leave the decoys in the truck...
Tomorrow is opening day, and I am hunting an open pasture (with my 5 year old daughter in tow).... I will use a jake/hen combo, cause it is one of the few open areas I hunt....