The narrowest Marathon Efficiency is 40mm so it's not a direct replacement for the discontinued Supremes. 40mm is wider than I need for the type of touring that I do, so unfortunately this tire is out for me.
In any case, looking at the Bicyclerollingresistance.com ranking chart, the Continental Contact Urban is a better tire overall than the Efficiency, with similar rolling resistance and weight but significantly better puncture resistance.
And there's also the Continental Grand Prix Urban. This tire is faster and lighter still, and given how cheap it is, it's a good choice for shorter tours where mid-tour tire replacement in developing countries isn't a factor.
And for any single leg tour without a mid tour flight, tubeless should be considered. None of these tires are tubeless.
Nope, I went to the rolling resistant site and they are both virtually the same with about 2 tenths of a watt separating the two, you would never ever remotely feel, or see the difference on any sort of bicycle watt meter.
Puncture wise the Urban is a bit better.
The Urban could be an interesting option, but what we don't know is how many miles will it last, but from the reports the Efficiency will last 6,000 to 8,000 miles, probably the lower number is loaded miles, the Urban I can only find a 6,000 mile rating and no word if that's loaded or not.
But the Urban tire won't work for me since it won't do well on a gravel road which sometimes I have to travel on.