This depends. Are you for sure entering the military match or are you considering civilian? If you're considering the ACGME match then you should take Step 1. If not, then you should not. Milmatch is based on a point system which you gain points for various aspects of your application (class rank/percentile, COMLEX/STEP percentile, amount and impact of research, etc). For the board score portion, they just look at your percentile for the exam you took and they do not compare the two. So for DOs it's usually beneficial to only take COMLEX unless you think you'll hit a higher percentile on Step (which is unlikely). If that happened I'm not sure if they would average the percentiles or not, but from what classmates told me it was more likely to hurt if you scored a lower percentile on Step after killing COMLEX, even if it was a solid Step score.
This is different for military medicine and those entering the milmatch are the only group I strongly recommend to not take Step 1 due to the above.