I was told by a friend of mine who used to be an electrician for SP years ago, that he hated working with Mars lights because there were about 17, or so, different wires to "play with". He said ditch lights only involved two.
I remember the first time I saw one of the first ATSF Red Warbonnet units with ditch lights at San Bernardino Depot as I was approaching on the road from the east. Not being used to them, it took me by surprise and I was a little shocked and confused, but it got my attention and it did make a difference in visibility of the front of the train.
I remember when the Amtrak 9600 series cab cars arrived for use in Southern California in the late 1980's This was before ditch lights requirements. Just having a headlight only on those cab cars were absolutely horrible. Several times I would approach a train with one in the lead that was stopped at a station at night to chat for a moment with the engine crew. Not having looked at it from the front while doing so, I would ask the crew if there headlight was turned on. They would say yes and I thought they were kidding me. I would then walk to the front and see the light on, but it just wasn't effective. In the mid 1990's, when Amtrak starting equipping these cars with ditch ligths, it was litterally the difference between night and day. You could see if the ditch lights were on at night from any angle. So, based upon that, I would have to say that I agree with current train and engine crews, that ditch lights are extremely effective and the way to go. I also agree that the flashing ditch light are not!