I have tried many - I find that the ELK Power bugle is the easiest and most reliable to use.
I have guided elk hunters for many years - you might want to know that you do not need to be a great caller - it is more about when to call/not call versus the sound you make. I had a friend open his truck door and throw up - and a bull elk answered the sound - ha ha.
Personally, I hardly ever call anymore... and if I do, it is to coax them in with a quiet cow call. When you bugle, you are competition for the other bulls in the area - and yes, they may answer, but it is very hard to get close to them. Better to know where they are moving and treestand hunt in my opinion/experience - I find a good spot (e.g., natural funnel) - and will sit there every morning and evening for as long as it takes (over the years, it has taken me from 3-38 sitting sessions to get a bull - average about 15)- This approach takes a ton of patience and is not for everyone, but it works every year for me.