I'm firmly in the camp that we should all take USMLE step 1. It's the better test of medical knowledge by far, and the nature of being a DO student is that there is a burden of proof that we're equivalent to our MD counterparts... especially if we are applying for ACGME residency positions.
But.... there are a few situations where it probably wouldn't be tactically beneficial, eg: 1) you're interested in a very competitive specialty and plan to apply AOA only, or 2) you're at risk of failing the USMLE Step 1 based on practice exams. If you truly have no idea what you want to do, and you take a few NBME practice tests and score well, why wouldn't you take Step 1 just to keep your options open?