If you have an H GTY, you might get an upgrade. No, I haven't seen those (smaller) cabins myself, but they are probably about the same size as a standard balcony cabin on Azamara.
Outside of your (very nice) small cabin, Splendor is a simply glorious ship. Wonderful service, great food, bars everywhere, what's not to like? We did do one Azamara trip and really enjoyed it, mainly because of the friendly attitude onboard (andwe did it in a Club Continent Suite, but saw the standard balcony cabin and thought it was adequate. I think you'll be happy with Regent.