the others pretty much spelled it out for ya. Personal prefference is the difference between mouth or E-callers. If predator hunting is something he will do often, then yes an E-caller would be a good thing to get. They hold all your sounds and it is just push and play. Mouth calls work well but you have to practice ALOT and hand calls require movement that the predator could see. What type of hunting, coyote population and other things will help him determine what he wants. If he decides on mouth calls then there is a Butt load of custom call makers that make very fine looking and working calls, I like customs better than mass. produced calls but again, personal preference. Kee's calls, THO gamecalls and bunches of others will set you up nice.

E-callers are like handcalls, everyone has what they like. I use a Wildlife Technology E-caller. It is the only e-caller that uses ALL REAL animal vocalizations. The remote out performs all others. It is by far the best you can get. Minaska makes a pretty good one and the remote works well, and then there are the rest.
There is NO magic pill when calling predators.