As someone who applied to 27 general surgery programs as a DO with only COMLEX scores and received interviews to only 7 programs (I was ranked to match at 2 programs for sure) and no VSLO auditions. I can say that if I could do it over again I would 100% take STEP because I was screened at many programs that I applied to. (Not that it matters because I ultimately decided to rank a few IM programs above the surgery programs due to location and overall vibe.)
If anyone who wants surgery or another competitive specialty sees this, suck it up and take STEP. I was lucky to have a good story, research, and grades to have gotten the interviews that I did and to have fallen in love with an IM subspecialty so it didnt matter in my situation ultimately. However you will be at an advantage if you eat the costs and take the extra exams.