1. Who is the man who is playing ball over there?
2. Who is the man that is playing ball over there?
我问老几位well-educated native speakers，他们说两句都对。
还有一人说第一句比第二句好。
可是台湾的国中参考书都是为了避免重复，第一句是不对的。
他们说没有这回事。不知各位先进看法如何?

Both are correct but I prefer the second one

任何人讲任何语言都会避免重复 但顶多作文被叫烂而已但不会说这样文法不对