I'd say in the field capacity they are very close, Maybe the 2166 is a little higher capacity.  But that is mostly opinion.

I never ran the 1480 much, it was Dad's combine and he preferred combining over trucking, so I hauled.   We had an 8 row corn head and Dad thought 3 MPH was plenty fast, so that's how fast he ran.  When we traded for the 2166 we didn't trade heads, just put them on the new one and ran the same speed.  When we traded for the 6 row we got him to run all the way to 4 MPH.  In my opinion he wasn't running either machine at capacity.

When Dad got sick and it became apparent I was going to be running the combine I started talking to folks with more experience than me for advice.  I asked the local dealership "combine guy" just how fast I should run with a 6 row head? He said "Awww ... if the corn is under 175 bushels I wouldn't run much over 6 miles an hour."

My response was along the lines of "No, seriously ..."  He was serious.

I don't know about ratings and classes and all that.  But my opinion is a 2166 will do anything a 1480 will and maybe a bit more.  And at the end of he day you won't be as tired.