I've used electronic (JS512 boat anchor). But I do better with my old Sceery variable pitch mouth caller. You can make a wide variety of sounds with a little practice. It only weighs 1 ounce & seems to call fox/bobcat better for me than the electronics. One thing I don't like about electronic calls is the fact that you must move more to place caller, find a hiding spot, then collect it before moving on. The mouth call is always there at the ready & makes me more stealthy. Besides, I get more satisfaction from calling them up myself. Maybe I'm missing the boat on quantity, but it works for me. Like others have said, spend $10 - $15 on a good mouth call, practice a little, & give it a try. You may surprise yourself. You don't have to spend $500 to effectively hunt predators, provided you have a weapon already.
Good luck,
HS