I find that I have more time as an adult than my daughter does. But to answer the original question, based on my experience I think adults and kids find different things easy when learning an instrument. I struggled with reading sheet music but when the teacher introduced it to my daughter she picked it up very quickly. Far faster than I did. And she is much better at hearing a phrase and, after learning the start of the phrase, figuring out how the rest of it goes on her own. However, when it came to good left and right hand technique (especially with a bow on the double bass) I was the "better student" so to speak. Of course, this could all be attributed to individual differences across age ranges rather than specifically differences in our ages.