My partner in Iraq used a Garmin 201 very effectively, but I carried a larger model garmin and a wrist watch. He snapped fast coords, and I did the precise stuff. It worked out well; he marked potential issues for mapping on routes, and I marked potential targets/friendlies when we could get into the locations. Unless load or efficiency is the primary concern, separate GPS from your watch is best. BTW, my watch was a Suunto Vector for as many ambient measurements I could get, along with a digital compass. It's amazing what the GPS will do just slightly larger than a pack of smokes.

After all that, I still carried an RFA map and compass. Never trust anything that requires batteries.