I'm also teaching a few Civil Engineering subjects in a local university in Sabah, fulltime, and almost all of my students are very young. Most of them came in after completing their STPM or matriculation and all with very short period, or probably no working experience in the industries. With the opportunity to teach engineering subjects to both group of students from different age and background, I'm able to observe several difference between matured and young students.
In general, I notice that matured students tend to be very serious when it comes to studying. They may be slow in grasping some information (due to the age factor), but they are very determined in trying to understand whatever it is taught. My opinion is that they value the importance of education. They invested their hard-earned money into education, because they know they are able to go far if they are able to improve in their academic achievements. They are able to see what they want in their future and education is the one of the main channels to achieve this.
Some students I teach in the university don't really know what they want in the future. If they can't be an engineer, they can be a teacher or whatever. Thus, the level of seriousness in learning is not as high as the matured students.
Matured students also tend to be vocal in class and with that, I find it easy to get their feedbacks. They are able to think critically, questioning any issues which they disagree on. With these kind of attitude, it is convenient for me as an educator to gauge my performance in teaching. I can improve my teaching method to achieve the purpose in getting them to appreciate the subject. If they don't understand something, say, a concept, they would just raise their hands and ask - without me asking them to. It is not so with young students. Most of the time, they will fall silent, that I have ask if they have any doubts etc just to get feedbacks. They also tend to be lost if I start to ask them questions which requires them to argue or think critically.
I can list more, but due to time constraint (it's almost 12.45 already), I'll just stop at two differences. Bear in mind that these are only my observation and I would understand if anyone disagree with me. Feel free to comment/argue with me in this issue. I would really like to learn from the experiences of others.