All the research points to one thing... wear earplugs if you are doing any riding at/over 60KM/H. That is when wind noise overcomes the sound of the bike and traffic. At highway speeds, you can't hear anything because of the wind noise. You will be less tired and more comfortable on your bike at highway speeds when you wear plugs.
I'm an audiologist, biker, and target shooter. I see the best and worst of both sides of noise. I wear custom protection when I am going to be doing any non-city riding.
Custom protection will always be best because it fits correctly and attenuates the same amount every time, where disposables are easy to insert incorrectly.