However, I suggest you study both of them. To do training, you must know something about human resources, otherwise a manager can't guide his subordinates' work without knowing this.
As far as the overall salary level is concerned, the salary of trainers is higher than that of human resources teachers and has greater potential. At the top of the trainer's career pyramid is a professional lecturer who will talk about the cost of a class.
I hope the above answers can help you, and I feel a little confused.