I agree with the statement that the best elk bugle is a cow call.
As far as bugles, about any call will work and it all depends on the mood of the elk, the way the hunter blows the call, the time of day, etc. Any of the elk calls on the market will work, or they wouldn't be selling them. I have had elk completely ignore me with one type of bugle, and then switch to a different sounding call and have all hell break loose.
I also agree that it has to be one that you can blow and make sound good. I've heard many hunters that sounded like a freaking wounded elephant screaming in pain...
a*r