The 15/16 are nearly identical and you can get a good one for less than your budget. My 2015 Ultra sold for about 26.5 on the dealer lot.
Some people had noise or rattle issues with the pano roof but with 3 cars, I never did. I also don't open it.
There were three models and the Ultimate has the 17 speaker stereo as well as other features. If you look at the difference with the present models, the packages are similar and you'll have a better idea of what to look for and what is important to you. The Ultimate cannot use Car Play or Android Auto if that is important to you, but you get the larger screen and Heads Up Display, a feature I really like. The AWD has features you don't need in Florida like a heated steering wheel and heated rear seats.
Not everyone agrees with me but if you are going to buy a luxury brand car, only one model suits me, the Ultimate. I'd rather have a full blown every option Sonata than a stripped down base model Genesis. Obviously, others disagree.