The first year I elk hunted, 2008, I got a bull to respond to a cow call well after the rut and stalked within 80 yds of him before his cows drew him away. The next day I got the same bull to respond to a bugle and took him down.
Last year I hunted the same are but wolves had moved in. There were still elk there but they responded to nothing. The weather was quite different so it's hard to draw conclusions.
I'll carry both, and try cow calling first.