Sanda is very practical, but it requires higher skills, and boxing requires higher strength.

If you spend a year, if you have a good understanding, teachers and hard work, you can learn both well.

As you said, if you are young, height and thinness are not very important issues. But when you are old, you should practice Sanda.

In short, Sanda focuses on technology, and boxing focuses on strength.

However, I still suggest you practice Sanda. As far as I know, I think it is much more practical than boxing.