I agree with your assessment! I have done the thermal suite on the Splendor and the Vista a couple of times, and on other lines. The main thing I didn't care for on the Vista was that the thermal tub (for lack of a better word) was right in the middle of the heated ceramic loungers, so it didn't really lend itself to a peaceful calming experience. People like to talk when they're in the tub, and if you're trying to relax on the lounger it can be distracting.
I much preferred the thermal suite on the Splendor, as the areas were separate, and made for a much more relaxing experience. Although as you said, if you had nothing to compare it to, you wouldn't know.