Power bugle is easiest and has really good sound I think. If you can master a mouth reed it is really versatile and nothing comes close.. does everything from calf, cow, small bull, herd bull and a host of other combinations. It really is the best call..if you can master it. I wouldn't waste my money on a hoochie mama.. they are prone to failure and really poorly built in my opinion. I know of 5 failures last year at the most critical times. Nothing as frustrating as a half arsed bleat/squeak from a call to cause a bull to bust outta the country just when you thought you had em. Once they fail you have to return them in original packaging, How many read the fine print?
I would choose the sleazy and cow in heat calls. Reliable as can be with external reed calls and very effective. The problem with reed calls, internal or external, is users blow from the mouth which is wet air instead of from deeper down which is dryer. Wet air causes the reed to fail and or sound "bubbly. Practice huffing from deeper in the chest like you are blowing up a balloon...you will notice a big difference.
Bugle to locate and cow call to work in. Or cow call only if you know you're close.