Diaphragms vary in ease. Like mentioned, single reeds are the easiest. Don't think you can't bugle with single reeds. You might not be the loudest, but it works.
I will tell you what I like. Bugling Bulls Mellow Yellow, All Star. Primos Ivory Palate Plate. I have some other multi reed calls, but I find I like these the best. I like them because I can cow call and slide the tube up to my mouth and bugle in a continuous sequence. (If I am trying to emulate a cow getting pestered by a bull). I use those reeds for locator bugles also. And since I bowhunt, a reed in the mouth to stop an animal is an advantage.