On our first trip, due to Radisson changing a previously booked trip, they gave us a Cat F and let us pay for a Cat H. On our next trip on Mariner, we paid for a Cat H guarantee and ended up in a Cat E. The next time, we paid for a Cat H guarantee and ended up in a Cat D. The first time we actually paid for anything higher than a Cat H on Mariner was PANDA as we were late booking so we paid for and received a Cat G )we waitlisted a Cat H guarantee but it never cleared).

On Voyager, we have always paid for and received Cat H but once on a guarantee we ended up in a Cat F.

I see no difference in either the Mariner or Voyager between Cat H through Cat D so why pay the extra money...

....at least my opinion. ;)