I agree with Lauren's opinion (in the comment column). For the sake of easy understandings, I recommend you to go through the followings URL. I have linked the result of Google image search. I think you will realize the difference. I hope it will be help for you! 玉 Tama https://goo.gl/J7qVX5 ボール Booru https://goo.gl/07Tnlm

I think Lauren is right. It is really good explanation for native. Basically, 玉 has broader meaning as it is 漢字. But I think ボール in Japanese has a little bit narrow meaning as Lauren said like ball for sports.

when ボール is used by itself, i think the first image that might appear in one's mind is like a sports ball such as a soccer ball or a tennis ball. but i think 玉 is more or less used to indicate a ball-shaped something. if you were to use 玉 in the context which ボール is appropriate, people might understand but could think it sounds strange. think of, for instance, when you want your friend to throw you a basketball but you ask to be thrown a sphere... i think it's the same kind of deal for 玉 and ボール. but that is just what i have accumulated from my experience. please get a second opinion from a native just to be certain :)