I agree with the Jeep Wrangler instead of a convertible in Hawaii. But only if i can get it at a reasonable price, otherwise we just get a more typical Chevy Impala, Buick Regal or similar. At least they have A/C and good size trunks, although it is just the two of us.
I burn easily, so even with a hat on I don't like to drive with the top down. We did enjoy the couple of times we rented a Jeep Wrangler (2-door) in Hawaii. We initially tried it with the top down, but too hot. So we just took the side and rear curtains down and left the top up. The top kept the heat off, but the open-air effect of the side curtains down was great. Wasn't going to try removing the doors on a rental, since no place to store them, but it would be fun to try.
While the Jeep does have a firm ride, I also certainly don't find it "uncomfortable". Not as smooth and powerful, with all the creature comforts known to man, as on my Infiniti M45X, but as DaveNW says, they are two completely different vehicles, also at two very different price points. But the Jeep is fun and I would pick it over a convertible anytime.
And for the OP, it doesn't matter what we think. It is what makes you happy and brings a smile to your face. That's why there are so many makes and models of cars. At $25 total difference for the rental, it is not an economic, but a purely personal decision. Have fun!