Welcome to the forum.
In my opinion it is good to have the steam-air decoking capability. This way you can decoke the heater without having to call an outside contractor to pig it. Depending of the location, it can take several weeks to get the pigging contractor to site. If you have an unplanned shutdown in the plant, you have the option to steam-air decoke the heater.
The link below can be helpful:
http://www.fwc.com/publications/tech_papers/files/NPRA2005%20FW%20Fired%20Heater%20Design%20%26%20Decoking%20Techniques%2Epdf
Regards,
CG
