That's a good question. I typically used twintail spyder or hula-type grubs when I am trying to mimic crabs or crawdads. I use singletail spyder or hula-type grubs when trying to mimic baitfish. I usually drag or hop the doubletails and swim the singletails. I have used single and doubles interchangeably too but my highest confidence is using them like I stated at the beginning.