It is all kind of relative. Since sound is actually a wave that bounces around, think of throwing a super ball around inside your truck. The less solid stuff it hits, the less it bounces. So, for drive train noises, a soft top or hard top with insulation will be best.
Then you have the exhaust just outside the cab. An insulated hard top is again the best since the bouncing ball can't get through to the inside because of the hard metal and the insulation keeps the ball hitting the metal noise down some too.
Wind noise to me seems about the same no matter the top. The big West Coast mirrors are a big contributor to wind noise compared to the smaller Elephant ears and down right tiny rectangular ones my Gasser has. That noise comes through the glass in the windows and doesn't really matter what top is on. If you have ever had a soft top come loose behind the cab while at speed, you will know what real noise is by the way. Once you get your pulse under control that is.
I only have a 1000 miles or so in M35 soft tops and hard tops. I like the hard top for noise and all weather use. But, those hard tops are heavy. Basically too heavy for one person to install or remove without scrathing stuff up. Part of the fun of these trucks is the convertible factor. A soft top wins hands down for ease of converting over for parades or just fall days in the sun driving.
But, here I sit 24-36 hours from a hurricane possibly being parked on top of my house and I just came in from prepping the Duece for possible rescue ops and I never once thought about my protection from the weather because I have the big heavy metal hard top on there.
Just trying to point out as many different angles on the tops as I can.