Well, if your goats lead very nicely, collars work well. If they don't lead well, the collar will sorta choke them and you won't have a lot of control over the goat. So for those ones, a halter would give greater control, control the head and you control the goat And halters will not choke them if that concerns you.
Funny story about that actually. I always keep collars on everyone all the time. But my little 7 month old baby girl louanne loves to walk horribly, and BOLT away towards the food! And then she insists on pulling me all the back to the gate. She is only going to get stronger so I put the halter on her for the first time the other day and she threw such a fit! She jumped off all fours, she put on the brakes, she threw herself on the ground, and yelled...very loudly lol. But I was very patient and calm and just stood there until she was done, and an hour or more later she walked right next to me in her halter lol give lots and lots of praise when they make progress!!