What are double-flat and single-flat soldering iron tips good for?
Butane irons are not meant for precision work where the difference between a pyramid or screwdriver tip and a conical tip make any difference.  If you are planning on electronics SMD work, the you really want a temperature controlled soldering station.  The cheapest decent one I know of is the Weller WE51, which is available for under $100 nowadays.

The advantage of butane is small, light, powerfuld, and portable to places without power.  Someone doing field service on remote telemetry stations, for example, might use one.  They are really not appropriate for something in a controlled lab environment with normal line power available.