It does matter what you put on. In a vol crush, double and triple calendars will likely lose if held through the earnings report. Single calendar can work if the price ends up near the strike, otherwise it will probably lose as well.
in a long run it doesnt matter -- your calendar's "vega" can be deceiving, if you dont know how it works
Calander's work great for some equities and horrible for others. That why you backtest and that why I made 100% on my SYMC double calander yesterday