Against all three types, the British shooters would come out on top because:
Against non shooting buildings, the British spend more time shooting them down over spending battle time moving around, trying to reach those buildings. With a +1 range and +15% DPS, they take out more buildings in their range before they have to move from their place towards other targets. They spend less time moving about, and more time shooting, because they can shoot at more targets from their current position on the base.
Against shooting buildings, yes, they have better survival, as you've rightly said.
Against defenders, the ability to start shooting at them earlier, due to +1 range, along with a +15% damage, before the defenders can even start shooting back, more than compensates for the ability to shoot twice as fast later.