As someone who spent at least 3 days minimum at each of those properties last summer, here's my ranking/thoughts:

1. Park Hyatt Abu Dhabi - This was the highlight of my visit in Abu Dhabi. The beach was beautiful, food choices were amazing, and the staff here really went above and beyond to make my stay memorable. It's beachfront anyway. Gym was a plus. Globalist upgrade to suite. A ton of Brits and europeans were here vacationing/partying.
2. Grand Hyatt Abu Dhabi - Huge building, right in the center. I liked their exterior, pool was meh... grand club/lounge was endless for happy hour, breakfast options were on point! Did not use the gym here. Globalist upgrade to suite. Pretty laid back, clientele was mainly british/american.
3. Andaz Capital Gate - Far, far away from any decent city center/activity/excursions to do. This hotel was primarily used by conference/business/ADNEC attendees. A steal on points/cash, breakfast buffet was really good, pool was pretty small, no sauna/steam/spa due to covid. Gym was available. Globalist upgrade to Suite. Clientele was all over the place.