Honestly, we really enjoyed the Grand Hyatt when we stayed there back in 2019. We didn't stay at the Regency so I can't compare but we've been to a few decent places around the world and for the price we paid (or points would have used), it really can't get a lot better. If you don't have any specifics that would push you to choose the Regency over the GH, I don't think you can go wrong here. I always use this GH as one end of my gauge for how many Hyatt points I have in my account as in, "This gets me x number of nights of Grand Hyatt Bali (or y nights at Park Hyatt Paris-Vendôme on the other end of the spectrum)." I start getting nervous when I can cover less than a month at GH Bali, so it's always a sort of reference point for me.