I do not like ecalls at all. I don't really use them at all for a few reasons... First setting them up moves a person further into the stand where the coyotes are more likely to see you or scent you. That is the primary reason. I also find that ecalls make me try to many sounds. I feel like picking 2 sounds a stand works better than anything.
I run hand calls. Prefer open reed call like the Dan Thompson Red desert howler. With that open reed I can make rabbit sounds, duck/goose sounds, high pitched squirrels/pdog sounds etc. I use that call with a coaxer call. I also really like bird sounds higher pitched rapid and excited calls.
The real key for calling coyotes is set up and location. You have to find places where you can hide the vehicle before getting into the area, a stand where you pop over an edge and sit down immediately. The longer and further you walk the more chance they will spot you. I prefer a cross wind at all cost and the ability to see down wind is a must. Almost all coyotes will try and circle the wind, especially the more mature dogs. Sometimes they come in fire and straight to the call, but usually they work around down wind.
Imagine where the coyotes are hunting in an area, the brushy bottoms, etc. Do not go into those areas, but set up on the edge of those areas and call them out. Again walking in gets you busted.
The ecallers are basically all the same, just some louder than others, some play dual sounds, etc. The real key is getting a stand where they do not know you are there, giving them a chance to approach where they are seen before getting wind.
Good luck. It is fun. A good day I will make 12-14 stands. I never call for more than 20 minutes a stand and keep moving. It is rare that I have a coyote show up later than 20 minutes. It seems most are there in 10 if they are coming.