The differences you cite between the Denon and the Yamaha simply do not exist in the non-subtle way you describe. Much, if not all, of the perceived can be attributed to "sight bias" -- your eyes have more influence over your perception of sound than you may realize -- and even very slight differences in the loudness of each device at the time you compared them.
Time and time again, perceived differences collapse to statistical insignificance when the testing is done in a controlled environment that minimizes as many variables as possible.
