If your intention is to specifically feed pretas and those in the bardo, do sur.
When Khandro Kamala, Chatral Rinpoche's Sangyum, was in the U.S. earlier this summer (and last summer as well), She did several different sang-chods followed by several different sur-chods followed by Protectors offerings each morning. During the sang, She made sure the fire was burning with visible flames. During sur, She made sure there were no visible flames but that there was a steady column of smoke. Also, She put somewhat different offerings in each.
IOW, these two practices each have their specific intentions and strong points. They are not identical and interchangeable. Of course, "If all you have is a hammer, everything looks like a nail." IMHO, if you specifically want to feed pretas and/or those in the bardo, receive transmission for sur. Pretty much any Lama can transmit this, and there are many, many short sur liturgies that are convenient and easy to do.
BTW, Lama Acharya Dawa Choddak will be in Boulder, CO Nov. 8-13. Among the teachings He will be giving, one night He will teach specifically on Riwo Sang-chod and another night He will be teaching on Barched Kunsel Nor-lha (Wealth Deity) Sang. I will post more information on these events in the Events section when I get more details.