PP Ultralinear VS PP Pentode

After reading the Carver threads , I became interested in what Mr. Carver was doing for a circuit
different from the masses . Unfortunately my expertise does not allow me to quite understand
his explanation for his circuit preference  .
So , I am asking for a description of the difference , in the final sound , of PP pentode as compared to PP ultralinear .
My present amp is PP Ultralinear , so I am familiar with that type of sound signature .

Thank You .