I have this idiot McGinnis on ignore so I missed his gibberish... there is no difference. An iron fly is equivalent to the call and put flies. The combo flies (straddle + strangle) are arb-equivalent to the natural flies (verts).
So my noob question would be: Why trade call and put flies and just trade the iron's? Whats the difference? Maybe its better to use call flys in you're playing for a pin at some higher price than spot. Puts if lower bias. Iron's for current spot price bet on the near future? Is this the right thinking?
In fact I'm reading @destriero older threads and your intraday trading weekly flies on AAPL etc... very interesting as I've never looked at weeekly flies. I'm trying to learn how you decide to structure these and what to look for when implementing flies... even calendars.