Headset question

I know there have been discussions before, but nothing turned up right
away in my searches.  Can someone explain the differences between
Sigtronics S-20, S-40, and S-45.  It looks like to me the performance
specs are roughly equal on them all.

From what I can tell the 40's are made slightly differently then the
20, and the 45 has the improved earcups over the 40.

But still all of these still roughly perform the same in terms of
weight and sound blocking?  Seems funny to me.

Just looking into getting my first pair of headsets, and just want
something for an fresh student pilot like myself.

Thanks for any help or advice.