I've been testing calendars vs. butterflies, and I find that calendars offer slightly better risk/reward, but lower probability. I'm using MSFT, comparing a July Call butterfly (29/33/37) vs. PUT Calendar (sell 33 July, buy 33 Aug). Is my observation true across the board, or is it related to another factor that it particular to this trade? Does anyone combine butterflies & calendars with the same short strike?