Is there a difference between??

one is hot and another is hottest.

Yes, a 16 year old is not an adult yet. I would say there is nothing wrong with a 16 year old and an 18 year old. But 24 is too much older. The 30 and the 38 year old are both mature adults by those ages.

Yes. The 16 year old is immature and the 24 year old if they want a 16 year old is immature. When you get older age differenc is not as big of a deal because you know what you want, you have lived through a lot and you can handle an adult relationship. A 16 yr old is still growing up and learning. They don't know how to handle a real adult relationship and the responsibilites that come with such.