I discovered the latter technique a few years ago, and have found it to be the most productive method I've ever used. However, if you're having motivation problems, try anything at least once, to see if it works. Take some food along, and give the dogs a bite when you call them and they come. Not strict obedience, mind you, but just an occasional goody for paying attention and coming when called. If your dog likes to fetch, take a ball, bumper, or other favorite object to play with.
Some dogs just like to play with the glove at the end of a track.
If one begins to lose interest in tracking, and the other one doesn't, then leave the slacker at home and take the worker to the field. Then, take the slacker next time. He might decide that he now wants to track, if that's the only way he gets to go. If your dog simply refuses to track, consider stopping the training for a while, especially if he's immature. Feed the dog a single normal day's ration at the end of the track in the field, or immediately afterwards in the car.