It's totally dependent on the specialty and if you plan on applying ACGME only, ACGME and AOA, or AOA only (in which case you probably wouldn't take the USMLE).
For example, in family medicine, a step 1 in the 200-210 range will open more doors for you than it shuts on the ACGME side, although if your level 1 is 500+, those same programs might accept that score with no step 1.
Radiology, for example, you need a step 1 for MOST programs, so a 210-220 is better than no step 1 with a 600+ level 1. I think a 210 will get you past the cutoff for about half of programs, whereas only about 10% or less of programs will accept a level 1 only. Even a 200-210 is better than a comlex only because you will make the cutoff for approximately a third of programs.
I think for most DO students, the threshold should be low to take step 1. Most students will be better off with a 210+ than no step 1 unless it's a very DO friendly field (PM&R, psych, FM) or they plan to match AOA.
On a related note, most pre-clinical students put a bit too much importance on the actual score. Many programs just want to see you have a minimum level of competence in standardized exams and won't fail specialty boards and other factors are more important such as the interview, dean's letter, LORs, personality and fit. For different specialties that minimum level of competence can mean different things because each specialty's exams are different... some specialties/programs just want a pass on all attempts, some want a 200+, others a 220+ etc.