The PdG is classic or belle epoque hotel from 1928 and has a very rich history. The PH is a very modern hotel with no history. So although the PH is a super nice hotel, I'll always choose the historical property. http://www.princedegallesparis.com/en/History

The PdG is quite a bit different from the Royal Hawaiian. It's a bit closer to the Palace in Madrid in its old-world style, but to a higher degree of quality.

Location wise for a tourist I don't think it matters. Both are very central. The PdG is next to the Four Seasons and it's nice to visit the bar or restaurant there.

Lastly I would say that the PdG is a very Parisian hotel. If you like French culture, this is the place. The PH could be almost anywhere in the world so if you don't appreciate French culture, maybe the PH is the best choice.