I have both. I’ve been with SPG for 8 years now vs 2 with Hyatt.

I would say it depends on the individual at each program. I had an amazing proactive Spg Ambassador, and then she left and my last one has been useless. The SPG folks on FT have been more helpful. As for Hyatt, I’ve only pinged her once and she was able to help resolve an issue immediately.

Ambassador/Concierge aside, I prefer Hyatt over SPG now and have moved all my stays over.