When I used to ride a Dyna (only one light up front, and a small one at that), I always rode during the day with the high beam on after noticing the same thing as Hunter; fewer folks pulling out in front of me. Now that I have a bike with spots, I just ride with the low beam and spots on at all times, and I get the same result of fewer folks pulling out or turning in front of me.
One suggestion I would make, if you run with spots on all the time make sure you aim them properly. They should be aimed at the same vertical dimension as the low beam headlight. I find it very irritating when another Harley rider is coming toward me with their spots aimed too high and angled toward the oncoming lane. We are looking for increased visibility, not increased irritation. There are enough folks who hate us without purposely creating more of them.
I've never tried a modulator, but I have seen several on other folks bikes and they do increase visibility. IMHO though, the low beam with spots is a better solution.
Jerry