While many of the techniques are similar, I think the main difference lies in motive. Namely, OMT is used as an adjunct to conventional medical treatment, whereas chiropractic tends to view nerve impingement as the root of disease and relieving nerve impingement as the motive for using their manipulations. OMT is more geared toward relieving muscle spasm, increasing drug efficacy (i.e. increasing blood flow), decreasing edema (i.e. mobilizing lymphatics,etc.), and freeing up limitations in a patients range of motion. I think it is fair to say that while the 2 schools of thought use very similar techniques much of the time, you may find DO's using them towards a different end than chiropracters. I am nor an expert on chiropractic by any means, so if I have misrepresented anything, I apologize.