Not sure about "why" the comparism, unless are you open to changing your current booking to have the time for a Tracy Arm add on??
They are completely different anyway. Prince William Sound is all glaciers, as you can see, 26 on your particular selection. This particular tour, with Phillips, does jump around a lot, but does also offer spectacular scenery. I do prefer another company which goes to few glaciers, but allows more time at the ones seen, including Ester Passage which is a definate highlight.
Tracy Arm is a very small portion glacier viewing. You do have the potential to see significantly more wildlife.